hnbgw: Change logging priorities and add HNBAP category

Log hnbap messages to the HNBAP category. Change MAIN category to only
log INFO and above and change SCTP notification message to debug.
diff --git a/src/hnbap_common.h b/src/hnbap_common.h
index bd8277b..ec214e9 100644
--- a/src/hnbap_common.h
+++ b/src/hnbap_common.h
@@ -131,7 +131,7 @@
 
 #include <osmocom/core/logging.h>
 
-#define HNBAP_DEBUG(x, args ...) DEBUGP(0, x, ## args)
+#define HNBAP_DEBUG(x, args ...) DEBUGP(1, x, ## args)
 
 extern int asn1_xer_print;