drm/edid: split CTA Y420VDB info and mode parsing

Separate the parsing of display info and modes from the CTA
Y420VDB. This is prerequisite work for overall better separation of the
two parsing steps.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/3bc5fe6650a6ce4249803f7192096764ea724e05.1672826282.git.jani.nikula@intel.com