drm/i915: Use single set of AUX powerwell ops for gen11+

AUX power wells sometimes need additional handling besides just
programming the specific power well registers:
 * Type-C PHY's also require additional Type-C register programming
 * ICL combo PHY's require additional workarounds
 * TGL & EHL combo PHY's can be treated like any other power well

Today we have dedicated aux ops for the ICL combo PHY and Type-C cases.
This works fine, but means that when a new platform shows up with
identical general power well handling, but different types of PHYs on
its outputs, we have to define an entire new power well table for that
platform and can't just re-use the table from the earlier platform -- as
an example, see ehl_power_wells[], which is a subset of
icl_power_wells[], *except* that we need to specify different AUX ops
for the third display.

If we instead create a single set of top-level aux ops that will check
the PHY type and then dispatch to the appropriate handlers, we can get
more reuse out of our power well definitions.  This allows us to
immediately eliminate ehl_power_wells[] and simply reuse the ICL table;
if future platforms follow the same general power well assignments as
either ICL or TGL, we'll be able to re-use those tables in the same way.

Note that I've only changed ICL+ platforms over to using the new icl_aux
ops; at this point it's unlikely that we'll have any new platforms that
re-use gen9 or earlier power well configurations.

v2:
 - ICL_AUX_PW_TO_PHY() won't return the proper PHY for TBT AUX power
   wells.  But we know those wells will only used on Type-C outputs
   anyway, so we can just check is is_tc_tbt flag in the condition.
   (Jose).

Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200415233435.3064257-2-matthew.d.roper@intel.com