drm/virtio: no need to pass virtio_gpu_ctrl_hdr

We can get it from vbuf.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20200205181955.202485-5-olvaffe@gmail.com


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>