net: mediatek: increase watchdog_timeo

During stress testing, after reducing the threshold value, we have seen
TX timeouts that were caused by the watchdog_timeo value being too low.
Increase the value to 5 * HZ which is a value commonly used by many other
drivers.

Signed-off-by: John Crispin <john@phrozen.org>
Signed-off-by: David S. Miller <davem@davemloft.net>