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/core/byteswap.h b/include/osmocom/core/byteswap.h
index 1f09c2b..4274b8f 100644
--- a/include/osmocom/core/byteswap.h
+++ b/include/osmocom/core/byteswap.h
@@ -2,7 +2,7 @@
 #include <stdint.h>
 #include <osmocom/core/endian.h>
 
-/*! \brief byte-swap a 32bit word
+/*! byte-swap a 32bit word
  *  \param[in] in to be swapped 32bit word
  *  \returns byte-swapped 32bit word */
 static inline uint32_t osmo_swab32(uint32_t in)
@@ -17,7 +17,7 @@
 	return out;
 }
 
-/*! \brief byte-swap a 16bit word
+/*! byte-swap a 16bit word
  *  \param[in] in to be swapped 16bit word
  *  \returns byte-swapped 16bit word */
 static inline uint16_t osmo_swab16(uint16_t in)