wifi: mt76: mt7996: set EHT max ampdu length capability

wifi: mt76: mt7996: set EHT max ampdu length capability

Set the max AMPDU length in the EHT MAC CAP. Without this patch, the
peer station cannot obtain the correct capability, which prevents
achieving peak throughput on the 2 GHz band.

Fixes: 1816ad9381e0 ("wifi: mt76: mt7996: add max mpdu len capability")
Signed-off-by: Peter Chiu <chui-hao.chiu@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Link: https://patch.msgid.link/20250515032952.1653494-3-shayne.chen@mediatek.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>