xenbus: prefer list_for_each()

This is more efficient than list_for_each_safe() when list modification
is accompanied by breaking out of the loop.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

drivers/xen/xenbus/xenbus_dev_frontend.c

@@ -364,7 +364,7 @@ static int xenbus_write_transaction(unsigned msg_type,
 
 static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
 {
-	struct watch_adapter *watch, *tmp_watch;
+	struct watch_adapter *watch;
 	char *path, *token;
 	int err, rc;
 	LIST_HEAD(staging_q);
@@ -399,7 +399,7 @@ static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
 		}
 		list_add(&watch->list, &u->watches);
 	} else {
-		list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
+		list_for_each_entry(watch, &u->watches, list) {
 			if (!strcmp(watch->token, token) &&
 			    !strcmp(watch->watch.node, path)) {
 				unregister_xenbus_watch(&watch->watch);