[PATCH] i386: Don't touch per cpu memory of offline CPUs in touch_nmi_watchdog

Just like on x86-64, don't touch foreign CPUs' memory if the watchdog
isn't enabled at all.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>