drm/xe/vf: Don't support MCR registers if VF

VF drivers can't operate on MCR registers.  Make sure that driver
is not trying to read nor write using any of MCR register.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240213154355.1221-9-michal.wajdeczko@intel.com