wifi: mt76: mt7921: fix ROC abort flow interruption in mt7921_roc_work

wifi: mt76: mt7921: fix ROC abort flow interruption in mt7921_roc_work

The mt7921_set_roc API may be executed concurrently with mt7921_roc_work,
specifically between the following code paths:

- The check and clear of MT76_STATE_ROC in mt7921_roc_work:
    if (!test_and_clear_bit(MT76_STATE_ROC, &phy->mt76->state))
        return;

- The execution of ieee80211_iterate_active_interfaces.

This race condition can interrupt the ROC abort flow, resulting in
the ROC process failing to abort as expected.

To address this defect, the modification of MT76_STATE_ROC is now
protected by mt792x_mutex_acquire(phy->dev). This ensures that
changes to the ROC state are properly synchronized, preventing
race conditions and ensuring the ROC abort flow is not interrupted.

Fixes: 034ae28b56f1 ("wifi: mt76: mt7921: introduce remain_on_channel support")
Cc: stable@vger.kernel.org
Signed-off-by: Quan Zhou <quan.zhou@mediatek.com>
Reviewed-by: Sean Wang <sean.wang@mediatek.com>
Link: https://patch.msgid.link/2568ece8b557e5dda79391414c834ef3233049b6.1769133724.git.quan.zhou@mediatek.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>