drm/xe: Remove GEN11 prefixes from documentation

The registers are already named without the GEN11 prefix. Do the same in
the memirq documentation.

Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Reviewed-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250306-drop-gen-v1-2-03683e56006a@intel.com


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