drm/xe/guc: Remove special handling for PVC A*

The rest of the driver doesn't really support PVC before B0 stepping.
Drop the special handling in xe_guc.c.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/20230504073250.1436293-4-lucas.demarchi@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>