drm/xe: Add XE_ENGINE_CLASS_OTHER to str conversion

drm/xe: Add XE_ENGINE_CLASS_OTHER to str conversion

XE_ENGINE_CLASS_OTHER was missing from the str conversion. Add it and
remove the default handling so it's protected by -Wswitch.
Currently the only user is xe_hw_engine_class_sysfs_init(), which
already skips XE_ENGINE_CLASS_OTHER, so there's no change in behavior.

Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240517204310.88854-3-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>