drm/i915/xelpd: Add XE_LPD power wells

Aside from the hardware-managed PG0, XE_LPD has power wells 1-2 and
A-D.  These power wells should be enabled/disabled according to the
following dependency tree (enable top to bottom, disable bottom to top):

               PG0
                |
             --PG1--
            /       \
          PGA     --PG2--
                 /   |   \
               PGB  PGC  PGD

PWR_WELL_CTL follows the general ICL/TGL design and places PG A-D in the
bits that would have been PG 6-9 under the old scheme.

PWR_WELL_CTL_{DDI,AUX}'s bit indexing for DDI's A-C and TC1 is the same
as TGL, but DDI-D is placed at index 7 (bits 14 & 15).

v2:
 - Squash in LPSP status patch from Uma since it's also a
   powerwell-specific change.

Bspec: 49233
Bspec: 49503
Bspec: 49504
Bspec: 49505
Bspec: 49296
Bspec: 50090
Bspec: 53920
Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210512042144.2089071-4-matthew.d.roper@intel.com