drm/edid: detect SCDC support in HF-VSDB

This patch does following:
- Adds a new structure (drm_hdmi_info) in drm_display_info.
  This structure will be used to save and indicate if sink
  supports advanced HDMI 2.0 features
- Adds another structure drm_scdc within drm_hdmi_info, to
  reflect scdc support and capabilities in connected HDMI 2.0 sink.
- Checks the HF-VSDB block for presence of SCDC, and marks it
  in scdc structure
- If SCDC is present, checks if sink is capable of generating
  SCDC read request, and marks it in scdc structure.

V2: Addressed review comments
 Thierry:
 - Fix typos in commit message and make abbreviation consistent
   across the commit message.
 - Change structure object name from hdmi_info -> hdmi
 - Fix typos and abbreviations in description of structure drm_hdmi_info
   end the description with a full stop.
 - Create a structure drm_scdc, and keep all information related to SCDC
   register set (supported, read request supported) etc in it.

Ville:
 - Change rr -> read_request
 - Call drm_detect_scrambling function drm_parse_hf_vsdb so that all
   of HF-VSDB parsing can be kept in same function, in incremental
   patches.

V3: Rebase.
V4: Rebase.
V5: Rebase.
V6: Rebase.
V7: Added R-B from Jose.
V8: Rebase.
V9: Rebase.
V10: Rebase.

Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1489404244-16608-4-git-send-email-shashank.sharma@intel.com