wifi: mt76: mt7921: handle MT7902 irq_map quirk with mutable copy

wifi: mt76: mt7921: handle MT7902 irq_map quirk with mutable copy

MT7902 PCIe requires a different wm2_complete_mask value, so introduce a
mutable per-device copy of the default irq_map and override the field
only for this chip. Other devices continue using the shared const
template.

This is a prerequisite patch before enabling MT7902 PCIe support.

Co-developed-by: Xiong Huang <xiong.huang@mediatek.com>
Signed-off-by: Xiong Huang <xiong.huang@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Link: https://patch.msgid.link/20260219004007.19733-3-sean.wang@kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>