watchdog: sch311x_wdt.c: Remove RESGEN

The SCH311x chip contains 2 watchdogs. One is the watchdog programmable
by the runtime register at address 0x65-0x68, the other is the watchdog
inside the power on reset generator. This second watchdog has a fixed
timeout value of ~1.6 seconds and is configurable only by the RESGEN
register.

The BIOS normally takes care of the RESGEN watchdog and disables it (at
least) before the OS is booted.

Unfortunately the sch311x_wdt driver clears bit 0 of the RESGEN register
which has the effect that at the latest 1.6 seconds later, a POR is
triggered.

The attached patch fixes this problem by completely removing any
reference to the RESGEN watchdog from the sch311x_wdt driver.

Signed-off-by: Dave Mueller <d.mueller@elsoft.ch>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>