ran_a_decode_cipher_mode_reject(): use gsm0808_get_cause()

Change-Id: I56dd920b931e769ba4d268b09700fe3c9fca4fc6
diff --git a/src/libmsc/ran_msg_a.c b/src/libmsc/ran_msg_a.c
index 6a33704..2890076 100644
--- a/src/libmsc/ran_msg_a.c
+++ b/src/libmsc/ran_msg_a.c
@@ -225,7 +225,7 @@
 		.msg_name = "BSSMAP Ciphering Mode Reject",
 	};
 
-	rc = gsm0808_get_cipher_reject_cause(tp);
+	rc = gsm0808_get_cause(tp);
 	if (rc < 0) {
 		LOG_RAN_A_DEC_MSG(LOGL_ERROR, "failed to extract Cause\n");
 		ran_dec_msg.cipher_mode_reject.bssap_cause = GSM0808_CAUSE_EQUIPMENT_FAILURE;