mac802154: iface: cleanup stack variable

There is no need to init res with zero, res can be unused but then we
returning zero and not res.

Signed-off-by: Alexander Aring <[e-mail]>
Signed-off-by: Marcel Holtmann <[e-mail]>

net/mac802154/iface.c

···
 {
 	struct ieee802154_sub_if_data *sdata = IEEE802154_DEV_TO_SUB_IF(dev);
 	struct ieee802154_local *local = sdata->local;
-	int res = 0;
+	int res;
 
 	ASSERT_RTNL();