watchdog: iTCO_wdt: Fix detection of SMI-off case

Obviously, the test needs to run against the register content, not its
address.

Fixes: cb011044 ("watchdog: iTCO_wdt: Account for rebooting on second timeout")
Cc: stable@vger.kernel.org
Reported-by: Mantas Mikulėnas <grawity@gmail.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Mantas Mikulėnas <grawity@gmail.com>
Link: https://lore.kernel.org/r/d84f8e06-f646-8b43-d063-fb11f4827044@siemens.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>