leds: apu: fix error message on probing failure

The current error message on failed probing tends to be a bit
misleading. Fix it to tell exactly that an APU v1 was not found.

Signed-off-by: Enrico Weigelt <info@metux.net>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>