Fix Memory leak

Memory associated with 'adv_data' will be leaked in case of
'generate_scan_rsp' failure
diff --git a/src/advertising.c b/src/advertising.c
index 441d0a2..b087b48 100644
--- a/src/advertising.c
+++ b/src/advertising.c
@@ -752,6 +752,7 @@
 	scan_rsp = generate_scan_rsp(client, &flags, &scan_rsp_len);
 	if (!scan_rsp && scan_rsp_len) {
 		error("Scan data couldn't be generated.");
+		free(adv_data);
 		return -EINVAL;
 	}