[WATCHDOG] ensure mouse and keyboard ignored in w83627hf_wdt

1. Ensure that the mouse and keyboard do not ping the watchdog.
This is the default operation of the w83627, but some BIOSes change this.

2. Increase the max timeout from 63 seconds to 255 seconds
as supported by the w83627 chip

3. Comment that the watchdog supports the w83627hg version of the chip

Signed-Off-By: Pádraig Brady <P@draigBrady.com>
Tested-by: Tomas Hodek <tomas.hodek@volny.cz>
Signed-Off-By: Wim Van Sebroeck <wim@iguana.be>