nvdimm/of_pmem: Convert to platform remove callback returning void

The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.

To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new(), which already returns void. Eventually after all drivers
are converted, .remove_new() will be renamed to .remove().

Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/8de0900f8c9f40648295fd9e2f445c85b2593d26.1712756722.git.u.kleine-koenig@pengutronix.deSigned-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

drivers/nvdimm/of_pmem.c

@@ -84,14 +84,12 @@ static int of_pmem_region_probe(struct platform_device *pdev)
 	return 0;
 }
 
-static int of_pmem_region_remove(struct platform_device *pdev)
+static void of_pmem_region_remove(struct platform_device *pdev)
 {
 	struct of_pmem_private *priv = platform_get_drvdata(pdev);
 
 	nvdimm_bus_unregister(priv->bus);
 	kfree(priv);
-
-	return 0;
 }
 
 static const struct of_device_id of_pmem_region_match[] = {
@@ -102,7 +100,7 @@ static const struct of_device_id of_pmem_region_match[] = {
 
 static struct platform_driver of_pmem_region_driver = {
 	.probe = of_pmem_region_probe,
-	.remove = of_pmem_region_remove,
+	.remove_new = of_pmem_region_remove,
 	.driver = {
 		.name = "of_pmem",
 		.of_match_table = of_pmem_region_match,