gprs_bssgp_rim: add value strings for enum bssgp_nacc_cause

Change-Id: I3354699555569c2b0bd1b4313cffd32a0cbeffe9
Related: SYS#5103
diff --git a/include/osmocom/gprs/gprs_bssgp_rim.h b/include/osmocom/gprs/gprs_bssgp_rim.h
index 7e9efcd..5e5966e 100644
--- a/include/osmocom/gprs/gprs_bssgp_rim.h
+++ b/include/osmocom/gprs/gprs_bssgp_rim.h
@@ -96,6 +96,12 @@
 	BSSGP_NACC_CAUSE_SIPSI_SET_ERR,
 };
 
+extern const struct value_string bssgp_nacc_cause_strs[];
+
+/*! Obtain a human-readable string for NACC Cause code */
+static inline const char *bssgp_nacc_cause_str(enum bssgp_nacc_cause val)
+{ return get_value_string(bssgp_nacc_cause_strs, val); }
+
 /* 3GPP TS 48.018, table 11.3.64.1.a, Application Error Container coding for NACC */
 struct bssgp_app_err_cont_nacc {
 	enum bssgp_nacc_cause nacc_cause;