drm/i915: Use pw_idx to derive PHY for ICL_LANE_ENABLE_AUX override

We don't actually know whether we should be picking the PHY
simply based on the AUX_CH/power well, or based on the VBT
defined AUX_CH->DDI->PHY relationship. At the moment we are
doing the former for the ANAOVRD workaround, and the latter
for the ICL_LANE_ENABLE_AUX override. Windows seems to use the
first approach for everything. So let's unify this to follow
that same approach for both.

Eventually we should try to figure out  which is actually
correct, or whether any of this even matters (ie. whether there
are any real machines where the DDI and its AUX_CH do not match
1:1).

Note that this also changes the behaviour if we do end up
poking an AUX power well not associated with any port (as
per VBT). Previously we would have skipped the PHY register
write, but now we always write it.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240229200357.7969-3-ville.syrjala@linux.intel.com


Reviewed-by: Imre Deak <imre.deak@intel.com>