[WATCHDOG] rc32434_wdt: fix watchdog driver

The existing driver code wasn't working. Neither the timeout was set
correctly, nor system reset was being triggered, as the driver seemed
to keep the WDT alive himself. There was also some unnecessary code.

Signed-off-by: Phil Sutter <n0-1@freewrt.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Cc: stable <stable@kernel.org>