watchdog: it8712f_wdt: Add module parameter for alternative reset sources

On iEi PCISA-9652-R10 (BIOS version 1.5) single board computer reads
from the game port do not seem to reset the watchdog timer. This patch
adds a module parameter wdt_config_reg to specify alternative reset
sources. At least WDT_RESET_KBD has been tested, even just running

while true; do
    setleds -L +scroll
    sleep 1
    setleds -L -scroll
    sleep 1
done

is enough to keep the watchdog happy.

Signed-off-by: Timo Juhani Lindfors <timo.lindfors@iki.fi>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>