of: overlay: pr_err from return NOTIFY_OK to overlay apply/remove

A device tree overlay notifier can return NOTIFY_OK, NOTIFY_STOP,
or an embedded errno.  overlay_notify() incorrectly reports an
error for NOTIFY_OK.

Reported-by: atull@kernel.org
Signed-off-by: NFrank Rowand <frank.rowand@sony.com>
Signed-off-by: NRob Herring <robh@kernel.org>

drivers/of/overlay.c

@@ -133,7 +133,7 @@ static int overlay_notify(struct overlay_changeset *ovcs,
 
 		ret = blocking_notifier_call_chain(&overlay_notify_chain,
 						   action, &nd);
-		if (ret == NOTIFY_STOP)
+		if (ret == NOTIFY_OK || ret == NOTIFY_STOP)
 			return 0;
 		if (ret) {
 			ret = notifier_to_errno(ret);