By moving update_display_info() out of _drm_edid_connector_update() we
make the function purely about adding modes. Rename accordingly.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/e9880bbb2b5724d9aac88a90a31ba3ba9af9da3f.1674144945.git.jani.nikula@intel.com