Add new log category 'ms'

This is useful to track the lifecycle of MS objects. The RLCMAC cateogry
used so far in those log messages is too broad.

Change-Id: Ib4ce88d0f7309ac77c064a94bb0d667e8dbc33dd
diff --git a/src/gprs_debug.h b/src/gprs_debug.h
index db9630c..b66de90 100644
--- a/src/gprs_debug.h
+++ b/src/gprs_debug.h
@@ -34,6 +34,7 @@
 	DRLCMACUL,
 	DRLCMACSCHED,
 	DRLCMACMEAS,
+	DMS,
 	DTBF,
 	DTBFDL,
 	DTBFUL,