drm: Add HDR source metadata property

This patch adds a blob property to get HDR metadata
information from userspace. This will be send as part
of AVI Infoframe to panel.

It also implements get() and set() functions for HDR output
metadata property.The blob data is received from userspace and
saved in connector state, the same is returned as blob in get
property call to userspace.

v2: Rebase and modified the metadata structure elements
as per Ville's POC changes.

v3: No Change

v4: Addressed Shashank's review comments

v5: Rebase.

v6: Addressed Brian Starkey's review comments, defined
new structure with header for dynamic metadata scalability.
Merge get/set property functions for metadata in this patch.

v7: Addressed Jonas Karlman review comments and defined separate
structure for infoframe to better align with CTA 861.G spec. Added
Shashank's RB.

v8: Addressed Ville's review comments. Moved sink metadata structure
out of uapi headers as suggested by Jonas Karlman.

v9: Rebase and addressed Jonas Karlman review comments.

v10: Addressed Ville's review comments, dropped the metdata_changed
state variable as its not needed anymore.

Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1558015817-12025-2-git-send-email-uma.shankar@intel.com