net/mlx4_core: Preparations for 802.1ad VLAN support

mlx4_core preparation to support hardware accelerated 802.1ad VLAN
device.

To allow 802.1ad accelerated device, "packet has vlan" (phv)
Firmware capability should be available. Firmware without the
phv capability won't behave properly and can't support 802.1ad device
acceleration.

The driver checks the Firmware capability and sets the phv bit
accordingly in SET_PORT command.

Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>