drm/xe/pf: Access VF's register using dedicated MMIO view

drm/xe/pf: Access VF's register using dedicated MMIO view

Instead of creating ad-hoc new register definitions with altered
register addresses to mimic the VF's access to these registers,
prepare new MMIO instance per required VF, with shifted internal
location of the register map.  This will allow to use unmodified
register definitions in all calls to xe_mmio() functions.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patch.msgid.link/20251024205826.4652-1-michal.wajdeczko@intel.com