drm/qxl: use drm_gem_object_funcs callbacks

Switch qxl to use drm_gem_object_funcs callbacks
instead of drm_driver callbacks.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: http://patchwork.freedesktop.org/patch/msgid/20190904054740.20817-6-kraxel@redhat.com