drm/xe: Wire up device shutdown handler

The system is turning off, and we should probably put the device
in a safe power state. We don't need to evict VRAM or suspend running
jobs to a safe state, as the device is rebooted anyway.

This does not imply the system is necessarily reset, as we can
kexec into a new kernel. Without shutting down, things like
USB Type-C may mysteriously start failing.

References: drm/i915/kernel#3500


Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
[mlankhorst: Add !xe_driver_flr_disabled assert]
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240905150052.174895-4-maarten.lankhorst@linux.intel.com