[WATCHDOG] Add w83697h_wdt early_disable option

Pádraig Brady requested the possibility of not disabling the watchdog
at module load time or kernel boot time if it had been previously enabled
in the bios. It may help rebooting the machine if it freezes before the
userland daemon kicks in.

Signed-off-by: Samuel Tardieu <sam@rfc1149.net>
Cc: Pádraig Brady <P@draigBrady.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>