linux-phytec-fsl

switchdev: assert rtnl mutex when going over lower netdevs

netdev_for_each_lower_dev has to be called with rtnl mutex held. So
better enforce it in switchdev functions.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>