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/include/osmocom/gsm/protocol/gsm_04_08.h b/include/osmocom/gsm/protocol/gsm_04_08.h
index 604a5df..90b6cf1 100644
--- a/include/osmocom/gsm/protocol/gsm_04_08.h
+++ b/include/osmocom/gsm/protocol/gsm_04_08.h
@@ -957,7 +957,7 @@
 
 #define GSM48_TA_INVALID 220
 
-/*! \brief Check if TA is valid according to 3GPP TS 44.018 § 10.5.2.40
+/*! Check if TA is valid according to 3GPP TS 44.018 § 10.5.2.40
  *  \param[in] ta Timing Advance value
  *  \returns true if ta is valid, false otherwise
  *  Note: Rules for GSM400 band are ignored as it's not implemented in practice.
@@ -1620,7 +1620,7 @@
 	GSM48_BCAP_MT_AUTO_1	= 8,
 };
 
-/*! \brief GSM 04.08 Bearer Capability: Speech Version Indication
+/*! GSM 04.08 Bearer Capability: Speech Version Indication
  *  (See also 3GPP TS 24.008, Table 10.5.103) */
 enum gsm48_bcap_speech_ver {
 	GSM48_BCAP_SV_FR	= 0,	/*!< GSM FR V1 (GSM FR) */