drm/xe/configfs: Use config_group_put()

configfs has a config_group_put() helper that was adopted by
commit 88df7939d7 ("drm/xe/configfs: Rename struct xe_config_device").
Another pending work to add psmi later landed in commit
afe902848b ("drm/xe/configfs: Allow to enable PSMI") and didn't use
the helper.

Use config_group_put() consistently to hide the inner workings of
configfs. No change in behavior since it does exactly the same thing
as currently being done.

Cc: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://lore.kernel.org/r/20250905162236.578117-2-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

drivers/gpu/drm/xe/xe_configfs.c

@@ -598,7 +598,7 @@ bool xe_configfs_get_psmi_enabled(struct pci_dev *pdev)
 		return false;
 
 	ret = dev->config.enable_psmi;
-	config_item_put(&dev->group.cg_item);
+	config_group_put(&dev->group);
 
 	return ret;
 }