wifi: mt76: mt7915: wed: enable red per-band token drop

Enable RED to limit the number of token used by each band. If single band
uses too many tokens, it would hurt the throughput of the other bands.The
software path can solve this problem by AQL so enable RED for HW path only.

Reviewed-by: Shayne Chen <shayne.chen@mediatek.com>
Signed-off-by: Peter Chiu <chui-hao.chiu@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>