virtio-mmio: Handle extra notification data

virtio-mmio: Handle extra notification data

Add support to virtio-mmio devices for handling the extra data sent from
the driver to the device when the VIRTIO_F_NOTIFICATION_DATA transport
feature has been negotiated.

The extra data that's passed to the virtio-mmio device when this feature
is enabled varies depending on the device's virtqueue layout.

The data passed to the virtio-mmio device is in the same format as the
data passed to virtio-pci devices.

Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Message-Id: <20240315165557.26942-4-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>