drm/xe: Fix comment on Wa_22013088509

On i915 the "see comment about Wa_22013088509" referred to the comment
in the graphics version >= 11 branch, where there were more details
about it. From the platforms supported by xe, only PVC needs
Wa_22013088509, but as the comment says, it's simpler to do it for all
platforms as there is no downside.  Bring the missing comment over from
i915 and reword it to fit xe better.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/20230504073250.1436293-3-lucas.demarchi@intel.com


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