drm/i915: Allow more varied alternate fixed modes for panels

drm/i915: Allow more varied alternate fixed modes for panels

On some systems the panel reports alternate modes with
different blanking periods. If the EDID reports them and VBT
doesn't tell us otherwise then I can't really see why they
should be rejected. So allow their use for the purposes of
static DRRS.

For seamless DRRS we still require a much more exact match
of course. But that logic only kicks in when selecting the
downclock mode (or in the future when determining whether
we can do a seamless refresh rate change due to a user
modeset).

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6374
Signed-off-by: Ville Syrjälä <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Reviewed-by: Jani Nikula <[email protected]>