drm/xe: Mark reserved engines in snapshot

When printing <debufs>/gt*/hw_engines, it's useful to mark
what engines are reserved so it doesn't mislead developers
while debugging.

Cc: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240906205609.3131330-1-lucas.demarchi@intel.com


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