drm/radeon/kms: improve pflip precision on r1xx-r4xx

The update pending bit has a separate enable bit.

Cc: Mario Kleiner <mario.kleiner@tuebingen.mpg.de>
Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
2 files changed