drm/edid: convert drm_parse_cea_ext() to use cea db iter

Iterate through all CTA data blocks across all CTA Extensions and
DisplayID data blocks.

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/7400792525c13f58652f288b891d6057637ed4c8.1651569697.git.jani.nikula@intel.com