gsm0480: Factor out msgb allocation helper function

Change-Id: If25b467481023eadaaf3f78157eceff4b81d24d2
diff --git a/include/osmocom/gsm/gsm0480.h b/include/osmocom/gsm/gsm0480.h
index e928d83..6a596ea 100644
--- a/include/osmocom/gsm/gsm0480.h
+++ b/include/osmocom/gsm/gsm0480.h
@@ -108,6 +108,8 @@
 int gsm0480_decode_ss_request(const struct gsm48_hdr *hdr, uint16_t len,
 				struct ss_request *request);
 
+struct msgb *gsm0480_msgb_alloc_name(const char *name);
+
 struct msgb *gsm0480_create_ussd_resp(uint8_t invoke_id, uint8_t trans_id, const char *text);
 struct msgb *gsm0480_create_unstructuredSS_Notify(int alertPattern, const char *text);
 struct msgb *gsm0480_create_notifySS(const char *text);