widget: use scanout offset when using virgl
widget: use scanout offset when using virgl

Ignoring the display area offset doesn't work nicely with virgl. Imho,
this condition is wrong even in QXL case.

Signed-off-by: Marc-André Lureau <a6f2b960a4aca61381fc650a67901b2ac8e83e6d@redhat.com>

fgouget/spice-gtk,fgouget/spice-gtk,flexVDI/spice-gtk,fgouget/spice-gtk,flexVDI/spice-gtk