drm/i915/xehp: handle new steering options

drm/i915/xehp: handle new steering options

Xe_HP is more modular than its predecessors and as a consequence it has
more types of replicated registers.  As with l3bank regions on previous
platforms, we may need to explicitly re-steer accesses to these new
types of ranges at runtime if we can't find a single default steering
value that satisfies the fusing of all types.

v2:
 - Add a local 'i915' variable to reduce gt->i915 usage.  (Caz)
 - Drop unused 'intel_gt_read_register' prototype.  (Caz)

v3:
 - Drop unnecessary comment text.  (Lucas)
 - Drop unused register bit definition.  (Lucas)

Bspec: 66534
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Caz Yokoyama <caz.yokoyama@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210729170008.2836648-2-matthew.d.roper@intel.com