drm/i915: don't rely on previous values set on DDI_BUF_CTL

Just set the only bit we need, everything else is either ignored on
HDMI or should be set to zero.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
1 file changed