PM: Improve error code of pm_notifier_call_chain()

This enables pm_notifier_call_chain() to get the actual error code
in the callback rather than always assume -EINVAL by converting all
PM notifier calls to return encapsulate error code with
notifier_from_errno().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
diff --git a/drivers/s390/char/vmwatchdog.c b/drivers/s390/char/vmwatchdog.c
index 12ef912..11312f4 100644
--- a/drivers/s390/char/vmwatchdog.c
+++ b/drivers/s390/char/vmwatchdog.c
@@ -258,13 +258,13 @@
 	if (test_and_set_bit(VMWDT_OPEN, &vmwdt_is_open)) {
 		pr_err("The system cannot be suspended while the watchdog"
 			" is in use\n");
-		return NOTIFY_BAD;
+		return notifier_from_errno(-EBUSY);
 	}
 	if (test_bit(VMWDT_RUNNING, &vmwdt_is_open)) {
 		clear_bit(VMWDT_OPEN, &vmwdt_is_open);
 		pr_err("The system cannot be suspended while the watchdog"
 			" is running\n");
-		return NOTIFY_BAD;
+		return notifier_from_errno(-EBUSY);
 	}
 	return NOTIFY_DONE;
 }