Introduce new BSSAP logging category/subsystem

Having all BSSAP related logs in the "DMSC" category is overly
generic, and dosn't provide useful granularity.

Change-Id: Id1e52dad03840dfd026fb23f3845a8771c8cc308
diff --git a/src/libcommon/debug.c b/src/libcommon/debug.c
index 8c0e787..fbdab80 100644
--- a/src/libcommon/debug.c
+++ b/src/libcommon/debug.c
@@ -122,6 +122,12 @@
 		.description = "Iu-CS Protocol",
 		.enabled = 1, .loglevel = LOGL_DEBUG,
 	},
+	[DBSSAP] = {
+		.name = "DBSSAP",
+		.description = "BSSAP Protocol (A Interface)",
+		.enabled = 1, .loglevel = LOGL_NOTICE,
+	},
+
 };
 
 static int filter_fn(const struct log_context *ctx, struct log_target *tar)