drm/vmwgfx: switch driver from bo->resv to bo->base.resv

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Thomas Hellstrom <thellstrom@vmware.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20190805140119.7337-13-kraxel@redhat.com