doxygen: enable AUTOBRIEF, drop \brief

Especially for short descriptions, it is annoying to have to type \brief for
every single API doc.

Drop all \brief and enable the AUTOBRIEF feature of doxygen, which always takes
the first sentence of an API doc as the brief description.

Change-Id: I11a8a821b065a128108641a2a63fb5a2b1916e87
diff --git a/src/gsm/gsm0808_utils.c b/src/gsm/gsm0808_utils.c
index 210f64e..34e10bb 100644
--- a/src/gsm/gsm0808_utils.c
+++ b/src/gsm/gsm0808_utils.c
@@ -44,7 +44,7 @@
  *  @{
  */
 
-/*! \brief Encode TS 08.08 AoIP transport address IE
+/*! Encode TS 08.08 AoIP transport address IE
  *  \param[out] msg Message Buffer to which to append IE
  *  \param[in] ss Socket Address to be used in IE
  *  \returns number of bytes added to \a msg */
@@ -88,7 +88,7 @@
 	return *tlv_len + 2;
 }
 
-/*! \brief Decode TS 08.08 AoIP transport address IE
+/*! Decode TS 08.08 AoIP transport address IE
  *  \param[out] ss Caller-provided memory where decoded socket addr is stored
  *  \param[in] elem pointer to IE value
  *  \param[in] len length of \a elem in bytes
@@ -223,7 +223,7 @@
 	return (uint8_t) (msg->tail - old_tail);
 }
 
-/*! \brief Encode TS 08.08 Speech Codec IE
+/*! Encode TS 08.08 Speech Codec IE
  *  \param[out] msg Message Buffer to which IE will be appended
  *  \param[in] sc Speech Codec to be encoded into IE
  *  \returns number of bytes appended to \a msg */
@@ -247,7 +247,7 @@
 	return *tlv_len + 2;
 }
 
-/*! \brief Decode TS 08.08 Speech Codec IE
+/*! Decode TS 08.08 Speech Codec IE
  *  \param[out] sc Caller-allocated memory for Speech Codec
  *  \param[in] elem IE value to be decoded
  *  \param[in] len Length of \a elem in bytes
@@ -328,7 +328,7 @@
 	return (int)(elem - old_elem);
 }
 
-/*! \brief Encode TS 08.08 Speech Codec list
+/*! Encode TS 08.08 Speech Codec list
  *  \param[out] msg  Message Buffer to which IE is to be appended
  *  \param[in] scl Speech Codec List to be encoded into IE
  *  \returns number of bytes added to \a msg */
@@ -363,7 +363,7 @@
 	return *tlv_len + 2;
 }
 
-/*! \brief Decode TS 08.08 Speech Codec list IE
+/*! Decode TS 08.08 Speech Codec list IE
  *  \param[out] scl Caller-provided memory to store codec list
  *  \param[in] elem IE value to be decoded
  *  \param[in] len Length of \a elem in bytes
@@ -408,7 +408,7 @@
 	return (int)(elem - old_elem);
 }
 
-/*! \brief Encode TS 08.08 Channel Type IE
+/*! Encode TS 08.08 Channel Type IE
  *  \param[out] msg Message Buffer to which IE is to be appended
  *  \param[in] ct Channel Type to be encoded
  *  \returns number of bytes added to \a msg */
@@ -450,7 +450,7 @@
 	return *tlv_len + 2;
 }
 
-/*! \brief Decode TS 08.08 Channel Type IE
+/*! Decode TS 08.08 Channel Type IE
  *  \param[out] ct Caller-provided memory to store channel type
  *  \param[in] elem IE Value to be decoded
  *  \param[in] len Length of \a elem in bytes
@@ -488,7 +488,7 @@
 	return (int)(elem - old_elem);
 }
 
-/*! \brief Encode TS 08.08 Encryption Information IE
+/*! Encode TS 08.08 Encryption Information IE
  *  \param[out] msg Message Buffer to which IE is to be appended
  *  \param[in] ei Encryption Information to be encoded
  *  \returns number of bytes appended to \a msg */
@@ -526,7 +526,7 @@
 	return *tlv_len + 2;
 }
 
-/*! \brief Decode TS 08.08 Encryption Information IE
+/*! Decode TS 08.08 Encryption Information IE
  *  \param[out] ei Caller-provided memory to store encryption information
  *  \param[in] elem IE value to be decoded
  *  \param[in] len Length of \a elem in bytes
@@ -565,7 +565,7 @@
 	return (int)(elem - old_elem);
 }
 
-/*! \brief Encode TS 08.08 Cell Identifier List IE
+/*! Encode TS 08.08 Cell Identifier List IE
  *  \param[out] msg Message Buffer to which IE is to be appended
  *  \param[in] cil Cell ID List to be encoded
  *  \returns number of bytes appended to \a msg */
@@ -604,7 +604,7 @@
 	return *tlv_len + 2;
 }
 
-/*! \brief Decode Cell Identifier List IE
+/*! Decode Cell Identifier List IE
  *  \param[out] cil Caller-provided memory to store Cell ID list
  *  \param[in] elem IE value to be decoded
  *  \param[in] len Length of \a elem in bytes
@@ -650,7 +650,7 @@
 	return (int)(elem - old_elem);
 }
 
-/*! \brief Convert the representation of the permitted speech codec identifier
+/*! Convert the representation of the permitted speech codec identifier
  *  that is used in struct gsm0808_channel_type to the speech codec
  *  representation we use in struct gsm0808_speech_codec.
  *  \param[in] perm_spch to be converted (see also gsm0808_permitted_speech)
@@ -687,7 +687,7 @@
 	return -EINVAL;
 }
 
-/*! \brief Extrapolate a speech codec field from a given permitted speech
+/*! Extrapolate a speech codec field from a given permitted speech
  *  parameter (channel type).
  *  \param[out] sc Caller provided memory to store the resulting speech codec
  *  \param[in] perm_spch value that is used to derive the speech codec info