leds: Fix wrong dmi_match on PC Engines APU LEDs

BIOS on APU board doesn't expose board_name property, and thus
we have to rely on the product_name instead.

Signed-off-by: Hans Ulli Kroll <ulli.kroll@googlemail.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>