arm: dts: mediatek: Fix pio-leds for Bananapi-R2

Pio-leds (near GPIO-Header) are swapped and LOW-active.
This patch restores the expected behaviour.

Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Reviewed-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>