mt76: mmio: introduce mt76x02_check_tx_hang watchdog

Port mt76x02_check_tx_hang watchdog from vendor driver in order to
perform a device reset when tx mac/dma logic hangs. Tx mac/dma stuck
has been observed when the device is heavy loaded or in a noisy
environment. Moreover introduce wdt delayed work in order to run
tx_hang watchdog. For the moment run mt76x02_check_tx_hang watchdog
just on mt76x2 devices since the issue has not been observed on mt76x0
driver yet

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>