drm/xe: fix engine_class bounds check again

drm/xe: fix engine_class bounds check again

This was fixed in commit b7dce525c4fc ("drm/xe/queue: fix engine_class
bounds check"), but then re-introduced in commit 6f20fc09936e ("drm/xe:
Move and export xe_hw_engine lookup.") which should only be simple code
movement of the existing function.

Fixes: 6f20fc09936e ("drm/xe: Move and export xe_hw_engine lookup.")
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Dominik Grzegorzek <dominik.grzegorzek@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240812141331.729843-2-matthew.auld@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>