drm/edid: add iterator for CTA data blocks

Add an iterator for CTA Data Blocks across EDID CTA Extensions and
DisplayID CTA Data Blocks.

v2: Update references, note why we can trust displayid ranges (Ville)

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/37fdd2d9eabc73aaa9f95c56246dc47aea0e8e4e.1651569697.git.jani.nikula@intel.com