x86: NMI watchdog: Downgrade helper

A downgrade helper for the NMI watchdog to be used in all places where
the I/O APIC watchdog may have been requested, but the I/O APIC is found
not to be there or meant to be left disabled.  This is so that the
reconfiguration is cosistent and defined in a single place only.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/asm-x86/nmi.h

@@ -78,6 +78,11 @@ extern int unknown_nmi_panic;
 void __trigger_all_cpu_backtrace(void);
 #define trigger_all_cpu_backtrace() __trigger_all_cpu_backtrace()
 
+static inline void localise_nmi_watchdog(void)
+{
+	if (nmi_watchdog == NMI_IO_APIC)
+		nmi_watchdog = NMI_LOCAL_APIC;
+}
 #endif
 
 void lapic_watchdog_stop(void);