drm/i915: Enable infoframes on GLK+ for HDR

This patch enables infoframes on GLK+ to be
used to send HDR metadata to HDMI sink.

v2: Addressed Shashank's review comment.

v3: Addressed Shashank's review comment.

v4: Added Shashank's RB.

v5: Dropped hdr_metadata_change check while modeset, as per
Ville's suggestion.

v6: Removed an unused and duplicate bit defintion, as per Ville's
comment.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
[mlankhorst: Reorder patch series]
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1558110145-3422-1-git-send-email-uma.shankar@intel.com