drm/i915: create a prepare phase for sprite plane updates

take out pin_fb code so the commit phase can't fail anymore.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
1 file changed