vmwgfx currently cannot support non-blocking commit because when
vmw_*_crtc_page_flip is called, drm_atomic_nonblocking_commit()
schedules the update on a thread.  This means vmw_*_crtc_page_flip
cannot rely on the new surface being bound before the subsequent
dirty and flush operations happen.

Cc: <stable@vger.kernel.org> # 4.12.x
Signed-off-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Charmaine Lee <charmainel@vmware.com>