virtio-blk: add host_features field in VirtIOBlock

virtio-blk: add host_features field in VirtIOBlock

Since configurable features for virtio-blk are growing, this patch
adds host_features field in the struct VirtIOBlock. (as in virtio-net)
In this way, we can avoid to add new fields for new properties and
we can directly set VIRTIO_BLK_F* flags in the host_features.

We update "config-wce" and "scsi" property definition to use the new
host_features field without change the behaviour.

Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20190221103314.58500-3-sgarzare@redhat.com
Message-Id: <20190221103314.58500-3-sgarzare@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>