x86: IO-APIC - use NMI_NONE instead of numeric constant

Not sure but maybe it is better to use NMI_DISABLED,
will take a look. But for now this patch is not change
anything in logic so it will not hurt/broke the kernel.
For most cases nmi_watchdog assignment is by one of NMI_*
macro so I think there it make sense too.
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/io_apic_32.c

@@ -2229,7 +2229,7 @@ static inline void __init check_timer(void)
 
 	if (nmi_watchdog == NMI_IO_APIC) {
 		printk(KERN_WARNING "timer doesn't work through the IO-APIC - disabling NMI Watchdog!\n");
-		nmi_watchdog = 0;
+		nmi_watchdog = NMI_NONE;
 	}
 	timer_ack = 0;
 

arch/x86/kernel/io_apic_64.c

@@ -1736,7 +1736,7 @@ static inline void __init check_timer(void)
 
 	if (nmi_watchdog == NMI_IO_APIC) {
 		printk(KERN_WARNING "timer doesn't work through the IO-APIC - disabling NMI Watchdog!\n");
-		nmi_watchdog = 0;
+		nmi_watchdog = NMI_NONE;
 	}
 
 	apic_printk(APIC_VERBOSE, KERN_INFO "...trying to set up timer as Virtual Wire IRQ...");