PM: Fix oops in suspend/hibernate code related to failing ioremap()

When ioremap() fails (which might happen for some reason), we nicely
oops in suspend_nvs_save() due to NULL dereference by memcpy() in there.
Fail gracefully instead.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/sleep.c

@@ -124,8 +124,7 @@ static int acpi_pm_freeze(void)
 static int acpi_pm_pre_suspend(void)
 {
 	acpi_pm_freeze();
-	suspend_nvs_save();
-	return 0;
+	return suspend_nvs_save();
 }
 
 /**
@@ -151,7 +150,7 @@ static int acpi_pm_prepare(void)
 {
 	int error = __acpi_pm_prepare();
 	if (!error)
-		acpi_pm_pre_suspend();
+		error = acpi_pm_pre_suspend();
 
 	return error;
 }