x86: Use this_cpu_inc_return for nmi counter

this_cpu_inc_return() saves us a memory access there.
Reviewed-by: NPekka Enberg <penberg@kernel.org>
Reviewed-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: NH. Peter Anvin <hpa@zytor.com>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NChristoph Lameter <cl@linux.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

arch/x86/kernel/apic/nmi.c

@@ -432,8 +432,7 @@ nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 		 * Ayiee, looks like this CPU is stuck ...
 		 * wait a few IRQs (5 seconds) before doing the oops ...
 		 */
-		__this_cpu_inc(alert_counter);
-		if (__this_cpu_read(alert_counter) == 5 * nmi_hz)
+		if (__this_cpu_inc_return(alert_counter) == 5 * nmi_hz)
 			/*
 			 * die_nmi will return ONLY if NOTIFY_STOP happens..
 			 */