[Not for upstream] drm/xe: add DPM_FLAG_SMART_SUSPEND

With commit: bca84a7 ("PM: sleep: Use DPM_FLAG_SMART_SUSPEND
conditionally"), DPM_FLAG_SMART_SUSPEND will only be used when the
devices parent and suppliers are all with the "smart suspend" feature
enabled. The feature is needed for Intel SoundWire links, SOF PCI
device is its parent and XE PCI is SOF PCI's link supplier.

Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>

Author: bardliao

drivers/gpu/drm/xe/xe_pci.c

@@ -860,6 +860,8 @@ static int xe_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (err)
 		goto err_driver_cleanup;
 
+	dev_pm_set_driver_flags(&pdev->dev, DPM_FLAG_SMART_SUSPEND);
+
 	drm_dbg(&xe->drm, "d3cold: capable=%s\n",
 		str_yes_no(xe->d3cold.capable));