vdpa: mask _F_CTRL_GUEST_OFFLOADS for vhost vdpa devices

QEMU does not emulate it so it must be disabled as long as the backend
does not support it.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20230602173328.1917385-1-eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>

net/vhost-vdpa.c

@@ -58,6 +58,7 @@ const int vdpa_feature_bits[] = {
     VIRTIO_F_VERSION_1,
     VIRTIO_NET_F_CSUM,
     VIRTIO_NET_F_GUEST_CSUM,
+    VIRTIO_NET_F_CTRL_GUEST_OFFLOADS,
     VIRTIO_NET_F_GSO,
     VIRTIO_NET_F_GUEST_TSO4,
     VIRTIO_NET_F_GUEST_TSO6,