drm/xe: Fix the runtime_idle call and d3cold.allowed decision.

According to Documentation/power/runtime_pm.txt:

int pm_runtime_put(struct device *dev);
    - decrement the device's usage counter; if the result is 0 then run
      pm_request_idle(dev) and return its result

int pm_runtime_put_autosuspend(struct device *dev);
    - decrement the device's usage counter; if the result is 0 then run
      pm_request_autosuspend(dev) and return its result

We need to ensure that the idle function is called before suspending
so we take the right d3cold.allowed decision and respect the values
set on vram_d3cold_threshold sysfs. So we need pm_runtime_put()
instead of pm_runtime_put_autosuspend().

Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Tested-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>