drm/edid: Use GTF2 for inferred modes

For some reason we only use the secondary GTF curve for the
standard timings. Use it for inferred modes as well.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220927170006.27855-6-ville.syrjala@linux.intel.com