doxygen: unify use of \file across the board

Considering the various styles and implications found in the sources, edit
scores of files to follow the same API doc guidelines around the doxygen
grouping and the \file tag.

Many files now show a short description in the generated API doc that was so
far only available as C comment.

The guidelines and reasoning behind it is documented at
https://osmocom.org/projects/cellular-infrastructure/wiki/Guidelines_for_API_documentation

In some instances, remove file comments and add to the corresponding group
instead, to be shared among several files (e.g. bitvec).

Change-Id: Ifa70e77e90462b5eb2b0457c70fd25275910c72b
diff --git a/include/osmocom/sim/sim.h b/include/osmocom/sim/sim.h
index eb95480..680cad1 100644
--- a/include/osmocom/sim/sim.h
+++ b/include/osmocom/sim/sim.h
@@ -1,3 +1,7 @@
+/*! \file sim.h
+ * Routines for helping with SIM (ISO/IEC 7816-4 more generally) communication.
+ */
+
 #ifndef _OSMOCOM_SIM_H
 #define _OSMOCOM_SIM_H
 
@@ -6,11 +10,6 @@
 
 #define APDU_HDR_LEN	5
 
-/*!
- * \file sim.h
- * Routines for helping with SIM (ISO/IEC 7816-4 more generally) communication.
- */
-
 /*! command-response pairs cases
  *
  * Enumeration used to identify the APDU structure based on command-response pair case , as specified in ISO/IEC 7816-3:2006(E) §12.1.