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/char/apm-emulation.c b/drivers/char/apm-emulation.c
index 548708c..a7346ab 100644
--- a/drivers/char/apm-emulation.c
+++ b/drivers/char/apm-emulation.c
@@ -606,7 +606,7 @@
 			return NOTIFY_OK;
 
 		/* interrupted by signal */
-		return NOTIFY_BAD;
+		return notifier_from_errno(err);
 
 	case PM_POST_SUSPEND:
 		/*