net/mlx4_en: Free netdev resources under state lock

Make sure mlx4_en_free_resources is called under the netdev state lock.
This is needed since RCU dereference of XDP prog should be protected.

Fixes: 326fe02d

 ("net/mlx4_en: protect ring->xdp_prog with rcu_read_lock")
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Reported-by: Sagi Grimberg <sagi@grimberg.me>
CC: Brenden Blanco <bblanco@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>