ipmi: use locks on watchdog timeout set on reboot

The IPMI watchdog timer clears or extends the timer on reboot/shutdown.
It was using the non-locking routine for setting the watchdog timer, but
this was causing race conditions.  Instead, use the locking version to
avoid the races.  It seems to work fine.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>