wifi: mt76: remove capability of partial bandwidth UL MU-MIMO

The firmware only supports full bandwidth UL MU-MIMO, so remove the
partial bandwidth capability from HE PHY CAP.

Signed-off-by: Howard Hsu <howard-yh.hsu@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Link: https://patch.msgid.link/20250515032952.1653494-1-shayne.chen@mediatek.com


Signed-off-by: Felix Fietkau <nbd@nbd.name>