wifi: mt76: mt7915: enable WED RX support

Enable RX Wireless Ethernet Dispatch available on MT7986 Soc in oreder
to offlad traffic received by WLAN NIC and forwarded to LAN/WAN one.

Tested-by: Daniel Golle <daniel@makrotopia.org>
Co-developed-by: Sujuan Chen <sujuan.chen@mediatek.com>
Signed-off-by: Sujuan Chen <sujuan.chen@mediatek.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>