drm: Add description for scdc variable

This patch adds description about 'scdc' variable in drm_hdmi_info
structure, to fix this warning during doc-build.

"drm_connector.h:140: warning: No description found for parameter 'scdc'"

V2: Rebase
V3: Added extra *
V4: Removed merged conflict
V5: Removed extra line at start of structure (Daniel)
V6: Make description single line (Daniel)

Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1490684779-21633-1-git-send-email-shashank.sharma@intel.com