drivers: intc_ite_it8xxx2: disable debug mode then reset for tests

After flashed EC image, we needed to manually press the reset button
on it8xxx2_evb. Now, without pressing the button, we can disable
debug mode and trigger a watchdog hard reset for running tests.

After flash EC, running below tests can pass (without pressing the button):
west build -p always -b it8xxx2_evb tests/drivers/watchdog/wdt_basic_api
west build -p always -b it8xxx2_evb tests/kernel/timer/timer_api
west build -p always -b it8xxx2_evb tests/kernel/fatal/exception

Signed-off-by: Dino Li <Dino.Li@ite.com.tw>
Signed-off-by: Ruibin Chang <Ruibin.Chang@ite.com.tw>