net/virtio: validate features at bus level

net/virtio: validate features at bus level

This patch provides a new callback for the bus type
to validate negotiated features are compatible with it.

Only user for now is PCI modern bus type, which implies
that the device supports Virtio 1.0+.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>