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>
diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index dc2c056..19a31f9 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -3421,6 +3421,7 @@
 		if (!text_ptr) {
 			pr_err("Unable to locate '=' string in text_in:"
 			       " %s\n", text_in);
+			kfree(payload);
 			return -EINVAL;
 		}
 		/*