doxygen: gsm: do not exclude include/gsm/protocol/*

Clear out the EXCLUDE tag to not exclude anything.

Tried to add API doc to gsm/protocol/gsm_08_08.h and after a long time found
out why they are not appearing in the API doc.

The original reason to exclude these files was that we were not going to
copy-paste descriptions from the 3GPP specs. Nevertheless, for an API doc
reader it is helpful if all data structures are listed and linked.

Change-Id: Ib569a46f00866bdaa4017f803d85f625ae011316
diff --git a/Doxyfile.gsm.in b/Doxyfile.gsm.in
index dbb5df6..896765e 100644
--- a/Doxyfile.gsm.in
+++ b/Doxyfile.gsm.in
@@ -654,7 +654,7 @@
 # against the file with absolute path, so to exclude all test directories
 # for example use the pattern */test/*
 
-EXCLUDE_PATTERNS       = */include/osmocom/gsm/protocol/*
+EXCLUDE_PATTERNS       =
 
 # The EXCLUDE_SYMBOLS tag can be used to specify one or more symbol names
 # (namespaces, classes, functions, etc.) that should be excluded from the