x86/nmi: remove spurious local_irq_enable from check_nmi_watchdog()

All callers of check_nmi_watchdog() already have local irqs enabled so
remove the unpaired local_irq_enable().

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Tim Deegan <tim@xen.org>

xen/arch/x86/nmi.c

@@ -126,7 +126,6 @@ int __init check_nmi_watchdog (void)
 
     for_each_online_cpu ( cpu )
         prev_nmi_count[cpu] = nmi_count(cpu);
-    local_irq_enable();
 
     /* Wait for 10 ticks.  Busy-wait on all CPUs: the LAPIC counter that
      * the NMI watchdog uses only runs while the core's not halted */