It attempted to avoid fps drops in the presence of cursor updates.  But
it is racing, and can result in hw updates after flush before vblank,
which leads to underruns.
Signed-off-by: NRob Clark <robdclark@chromium.org>
Reviewed-by: NSean Paul <sean@poorly.run>
Signed-off-by: NRob Clark <robdclark@chromium.org>