drm/xe: Allow to disable engines

drm/xe: Allow to disable engines

Sometimes it's useful to load the driver with a smaller set of engines
to allow more targeted debugging, particularly on early enabling.

Besides checking what is fused off in hardware, add similar logic to
disable engines in software. This will use configfs to allow users
to set what engine to disable, so already add prepare for that. The
exact configfs interface will be added later.

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20250528-engine-mask-v4-3-f4636d2a890a@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>