wifi: mt76: add WED RX support to mt76_dma_{add,get}_buf

Introduce the capability to configure RX WED in mt76_dma_{add,get}_buf
utility routines.

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>