drm/i915/dg1: Add DG1 power wells

TGL power wells can be re-used for DG1 with the exception of the fake
power well for TC_COLD.

v2: use logic to skip power wells while copying instead of duplicating
the definition of TGL power wells (Matt Roper)

Bspec: 49182

Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201014191937.1266226-3-lucas.demarchi@intel.com