wifi: mt76: mt7921: fix a potential association failure upon resuming

In multi-channel scenarios, the granted channel must be aborted before
suspending. Otherwise, the firmware will be put into a wrong state,
resulting in an association failure after resuming.
With this patch, the granted channel will be aborted before suspending
if necessary.

Signed-off-by: Leon Yen <leon.yen@mediatek.com>
Signed-off-by: Ming Yen Hsieh <mingyen.hsieh@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>