llc: Avoid propagating rc=1

Those functions guarantee to the caller that the prim is always freed,
and hence returning 1 has not meaning there.

Fix similar to bab234c2ea in rlcmac layer.

Change-Id: Icdee1cac4df970ae2ee7539d72c5a82667016160

src/llc/llc_prim.c

@@ -183,6 +183,8 @@ int gprs_llc_prim_call_down_cb(struct osmo_gprs_llc_prim *llc_prim)
 	/* Special return value '1' means: do not free */
 	if (rc != 1)
 		msgb_free(llc_prim->oph.msg);
+	else
+		rc = 0;
 	return rc;
 }
 
@@ -212,5 +214,7 @@ int osmo_gprs_llc_prim_lower_up(struct osmo_gprs_llc_prim *llc_prim)
 	/* Special return value '1' means: do not free */
 	if (rc != 1)
 		msgb_free(msg);
+	else
+		rc = 0;
 	return rc;
 }