mrf24j40: add random extended addr generation

The mrf24j40 has no source to get a permanent extended address. This
patch will add a random generated permanent extended address source.

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>

drivers/net/ieee802154/mrf24j40.c

@@ -722,6 +722,7 @@ err_ret:
 
 static void  mrf24j40_phy_setup(struct mrf24j40 *devrec)
 {
+	ieee802154_random_extended_addr(&devrec->hw->phy->perm_extended_addr);
 	devrec->hw->phy->current_channel = 11;
 }