mt76: mt7921: reduce the mutex lock scope during reset

Reduce the mutex lock scope for reset to get rid of possible task hung
e.g wpa_supplicant and to allow the user-space process to keep running
during we need more retries to complete the reset.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Suggested-by: YN Chen <YN.Chen@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>