drm/i915: Preparations for enabling P010, P012, P016 formats

Preparations for enabling P010, P012 and P016 formats. These
formats will extend NV12 for larger bit depths.

Signed-off-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Signed-off-by: Swati Sharma <swati2.sharma@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1551700595-21481-3-git-send-email-swati2.sharma@intel.com