watchdog: iTCO_wdt: Account for rebooting on second timeout

This was already attempted to fix via 1fccb730

: If the BIOS did not
enable TCO SMIs, the timer definitely needs to trigger twice in order to
cause a reboot. If TCO SMIs are on, as well as SMIs in general, we can
continue to assume that the BIOS will perform a reboot on the first
timeout.

QEMU with its ICH9 and related BIOS falls into the former category,
currently taking twice the configured timeout in order to reboot the
machine. For iTCO version that fall under turn_SMI_watchdog_clear_off,
this is also true and was currently only addressed for v1, irrespective
of the turn_SMI_watchdog_clear_off value.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/0b8bb307-d08b-41b5-696c-305cdac6789c@siemens.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>