x86: touch_nmi_watchdog(): reset alert counters for supported nmi_watchdog modes only

The checking 'if nmi_watchdog > 0' (ie NMI_NONE) is quite fast but it
has a side effect - it's taken even if nmi_watchdog = NMI_DISABLED.

Nowadays nmi_watchdog is set up to NMI_NONE by default so this condition
is properly taken most the time but we better show this explicitly.
Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/nmi.c

@@ -354,7 +354,8 @@ static DEFINE_PER_CPU(int, nmi_touch);
 
 void touch_nmi_watchdog(void)
 {
-	if (nmi_watchdog > 0) {
+	if (nmi_watchdog == NMI_LOCAL_APIC ||
+		nmi_watchdog == NMI_IO_APIC) {
 		unsigned cpu;
 
 		/*