wifi: mt76: mt7921: fix using incorrect group cipher after disconnection.

wifi: mt76: mt7921: fix using incorrect group cipher after disconnection.

To avoid incorrect cipher after disconnection, we should
do the key deletion process in this case.

Fixes: e6db67fa871d ("wifi: mt76: ignore key disable commands")
Signed-off-by: Michael Lo <michael.lo@mediatek.com>
Signed-off-by: Ming Yen Hsieh <mingyen.hsieh@mediatek.com>
Tested-by: David Ruth <druth@chromium.org>
Reviewed-by: David Ruth <druth@chromium.org>
Link: https://patch.msgid.link/20240801024335.12981-1-mingyen.hsieh@mediatek.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>