iscsi-target: missing kfree() on error path

Fix-up breakage in iscsit_build_sendtargets_response() from v3.11
changes, and free "payload" before returning.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/iscsi/iscsi_target.c

@@ -3421,6 +3421,7 @@ static int iscsit_build_sendtargets_response(struct iscsi_cmd *cmd)
 		if (!text_ptr) {
 			pr_err("Unable to locate '=' string in text_in:"
 			       " %s\n", text_in);
+			kfree(payload);
 			return -EINVAL;
 		}
 		/*