net/mlx4_core: Add basic elements for QCN

Add device capability, firmware command opcode and etc prior elements
needed for QCN suppprt. Disable SRIOV VF view/access for QCN is disabled.

While here, remove a redundant offset definition into the
QUERY_DEV_CAP mailbox.

Signed-off-by: Shani Michaeli <shanim@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>