drm/edid: detect basic audio in all CEA extensions

Convert drm_find_cea_extension() to EDID block iterator in basic audio
detection. Detect basic audio in all CEA extensions.

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/59481d0397de4b91b3e6ea665882334e92538f40.1651569697.git.jani.nikula@intel.com