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/sim/core.c b/src/sim/core.c
index 1ce2fed..15a1563 100644
--- a/src/sim/core.c
+++ b/src/sim/core.c
@@ -210,7 +210,7 @@
 }
 
 
-/*! \brief Generate an APDU message and initialize APDU command header
+/*! Generate an APDU message and initialize APDU command header
  *  \param[in] cla CLASS byte
  *  \param[in] ins INSTRUCTION byte
  *  \param[in] p1 Parameter 1 byte