sony-laptop: brightness regression fix

After commit 540b8bb9:

  sony-laptop: fingers off backlight if video.ko is serving this functionality

I can't set brightness on my sony laptop (nothing in /sys/class/backlight).
dmesg says "sony-laptop: Sony: Brightness ignored, must be controlled by ACPI
video driver".

The function acpi_video_backlight_support returns 0 if we should use the
vendor-specific backlight support, while non-0 if the ACPI generic should
be used. Because of this, the check introduced by the said commit appears
reversed.
Signed-off-by: NAlessandro Guido <ag@alessandroguido.name>
Signed-off-by: NLen Brown <len.brown@intel.com>

drivers/misc/sony-laptop.c

@@ -1038,7 +1038,7 @@ static int sony_nc_add(struct acpi_device *device)
 		goto outinput;
 	}
 
-	if (!acpi_video_backlight_support()) {
+	if (acpi_video_backlight_support()) {
 		printk(KERN_INFO DRV_PFX "Sony: Brightness ignored, must be "
 		       "controlled by ACPI video driver\n");
 	} else if (ACPI_SUCCESS(acpi_get_handle(sony_nc_acpi_handle, "GBRT",