mt76: mt7921: fix the base of PCIe interrupt

Should use 0x10000 as the base to operate PCIe interrupt according
to the vendor reference driver.

Fixes: ffa1bf97 ("mt76: mt7921: introduce PM support")
Co-developed-by: YN Chen <YN.Chen@mediatek.com>
Signed-off-by: YN Chen <YN.Chen@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Tested-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>