wifi: mt76: mt7996: add max mpdu len capability

wifi: mt76: mt7996: add max mpdu len capability

Set max mpdu len to 11454 according to hardware capability.
Without this patch, the max ampdu length would be 3895 and count not get
expected performance.

Fixes: 348533eb968d ("wifi: mt76: mt7996: add EHT capability init")
Signed-off-by: Peter Chiu <chui-hao.chiu@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Link: https://patch.msgid.link/20250114101026.3587702-1-shayne.chen@mediatek.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>