net/mlx5e: Rely on rcu instead of rtnl lock when getting upper dev

Function netdev_master_upper_dev_get() generates warning if caller doesn't
hold rtnl lock. Modify rules update path to use rcu version of that
function.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Reviewed-by: Jianbo Liu <jianbol@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>