sony-laptop: fix bogus error message display on resume

sony_backlight_update_status returns 0 on success -1 on failure (i.e.: the
return value from acpi_callsetfunc. The return value in the resume path
was broken and thus always displaying a bogus warning about not being able
to restore the brightness level.
Signed-off-by: Mattia Dongili <malattia@linux.it>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/platform/x86/sony-laptop.c

@@ -1041,7 +1041,7 @@ static int sony_nc_resume(struct acpi_device *device)
 
 	/* set the last requested brightness level */
 	if (sony_backlight_device &&
-			!sony_backlight_update_status(sony_backlight_device))
+			sony_backlight_update_status(sony_backlight_device) < 0)
 		printk(KERN_WARNING DRV_PFX "unable to restore brightness level\n");
 
 	return 0;