drm/xe: Enable D3Cold on 'low' VRAM utilization

drm/xe: Enable D3Cold on 'low' VRAM utilization

Now that we eliminated all the mem_access get/put with its
locking issues from the inner calls of migration, we can
allow D3Cold.

Enable it when VRAM utilization is lower then 300Mb. On
higher utilization we only allow D3hot so we don't increase
so much the latency on runtime resume due to the memory
restoration.

Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240522170105.327472-7-rodrigo.vivi@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>