soc: mediatek: pwrap: add arbiter capability

Add arbiter capability for pwrap driver.
The arbiter capability uses new design to judge the priority and latency
for multi-channel.
The design with arbiter support cannot change the watchdog timer.
This patch is preparing for adding mt6873/8192 pwrap support.

Signed-off-by: Hsin-Hsiung Wang <hsin-hsiung.wang@mediatek.com>
Link: https://lore.kernel.org/r/1615563286-22126-3-git-send-email-hsin-hsiung.wang@mediatek.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>