drm/i915: Call i915_gem_suspend() only after display is turned off

When the last reference of a gem object is removed it is added to the
mm.free_list list and mm.free_work is queued to actually free the
object.

So gem objects that had their last reference removed by display during
drm_atomic_helper_shutdown() are added to mm.free_list what could
cause that mm.free_work is executed at the same time as
intel_runtime_pm_driver_release() causing raw-wakerefs warning.

So here only calling i915_gem_suspend() and by consequence
i915_gem_drain_freed_objects() only after display is down making
sure all display gem objecs are freed when
intel_runtime_pm_driver_release() is executed.

Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220617190629.355356-1-jose.souza@intel.com