ieee802154: 6lowpan: remove check on null

This patch removes one check on null which should be already done by
checking before for ARPHRD_IEEE802154. All ARPHRD_IEEE802154 and
ARPHRD_IEEE802154_MONITOR should have wdev->ieee802154_ptr, where
ARPHRD_IEEE802154 is currently a node interface only.

Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/ieee802154/6lowpan/core.c

@@ -214,7 +214,7 @@ static int lowpan_device_event(struct notifier_block *unused,
 		 * also delete possible lowpan interfaces which belongs
 		 * to the wpan interface.
 		 */
-		if (wdev->ieee802154_ptr && wdev->ieee802154_ptr->lowpan_dev)
+		if (wdev->ieee802154_ptr->lowpan_dev)
 			lowpan_dellink(wdev->ieee802154_ptr->lowpan_dev, NULL);
 		break;
 	default: