Add parse_irq to handle that interrupt status structure is
different between mt7663s and mt7921s.

This is a preliminary patch to introduce mt7921s driver
Tested-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>