We can't be within an RCU read-side critical section when deleting
VLANs, as underlying drivers might sleep during the hardware operation.
Therefore, replace the RCU critical section with a mutex. This is
consistent with team_vlan_rx_add_vid.

Fixes: 3d249d4c ("net: introduce ethernet teaming device")
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>