UPSTREAM: drm: virtio-gpu: transfer dumb buffers to host on plane update

For dumb buffers, we need to transfer them to the host when updating a
plane.

Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>
(cherry picked from commit 4109e7f7d5aeefaa1d72f9ab4c63aa5d79fc81fb)

Change-Id: I125ccb3943d82ac1a7738e2afde28eea9e55abcc
Signed-off-by: Alistair Strachan <astrachan@google.com>