wl12xx: implement SW Tx watchdog

Track freed FW blocks during Tx. If no blocks were freed during a
predefined timeout, initiate a HW recovery. This helps in situations
when the FW watchdog fails.

Don't trigger recovery during activities that can temporarily stop
Tx. This includes:
- scanning
- buffering packets for sleeping stations (AP role)
- ROC on any role

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>