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/gsmtap_util.h b/include/osmocom/core/gsmtap_util.h
index 2e3d068..b60257e 100644
--- a/include/osmocom/core/gsmtap_util.h
+++ b/include/osmocom/core/gsmtap_util.h
@@ -19,14 +19,14 @@
 			    uint8_t ss, uint32_t fn, int8_t signal_dbm,
 			    uint8_t snr, const uint8_t *data, unsigned int len);
 
-/*! \brief one gsmtap instance */
+/*! one gsmtap instance */
 struct gsmtap_inst {
-	int ofd_wq_mode;	/*!< \brief wait queue mode? */
-	struct osmo_wqueue wq;	/*!< \brief the wait queue */
-	struct osmo_fd sink_ofd;/*!< \brief file descriptor */
+	int ofd_wq_mode;	/*!< wait queue mode? */
+	struct osmo_wqueue wq;	/*!< the wait queue */
+	struct osmo_fd sink_ofd;/*!< file descriptor */
 };
 
-/*! \brief obtain the file descriptor associated with a gsmtap instance
+/*! obtain the file descriptor associated with a gsmtap instance
  *  \param[in] gti GSMTAP instance
  *  \returns file descriptor of GSMTAP instance */
 static inline int gsmtap_inst_fd(struct gsmtap_inst *gti)