Add Virtio Emulation related fields to the device capabilities.

It includes a general bit to indicate whether Virtio Emulation is
supported and the capabilities structure itself.
Signed-off-by: NYishai Hadas <yishaih@mellanox.com>
Reviewed-by: NShahaf Shuler <shahafs@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>