drm/i915: Set the Z inversion overlap field

Dual link Z-inversion overlap field is present
in MIPI_CTRL register unlike the older platforms,
hence setting the same in this patch.

Signed-off-by: Deepak M <m.deepak@intel.com>
Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1487078180-15147-5-git-send-email-madhav.chauhan@intel.com