virtio-gpu: splitting one extended mode guest fb into n-scanouts

virtio-gpu: splitting one extended mode guest fb into n-scanouts

When guest is running Linux/X11 with extended multiple displays mode enabled,
the guest shares one scanout resource each time containing whole surface
rather than sharing individual display output separately. This extended frame
is properly splited and rendered on the corresponding scanout surfaces but
not in case of blob-resource (zero copy).

This code change lets the qemu split this one large surface data into multiple
in case of blob-resource as well so that each sub frame then can be blitted
properly to each scanout.

v2: resizing qemu console in virtio_gpu_update_dmabuf to scanout's width and
    height

v3: updating stub function of virtio_gpu_update_dmabuf to match the type

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Message-Id: <20211104065153.28897-5-dongwon.kim@intel.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>