x86/nmi: Fix timeout test in test_nmi_ipi()

We're supposed to exit the loop with "timeout" set to zero.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-janitors@vger.kernel.org
Fixes: 99e8b9ca ("x86, NMI: Add NMI IPI selftest")
Link: http://lkml.kernel.org/r/20170619105304.GA23995@elgon.mountainSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/nmi_selftest.c

@@ -78,7 +78,7 @@ static void __init test_nmi_ipi(struct cpumask *mask)
 
 	/* Don't wait longer than a second */
 	timeout = USEC_PER_SEC;
-	while (!cpumask_empty(mask) && timeout--)
+	while (!cpumask_empty(mask) && --timeout)
 	        udelay(1);
 
 	/* What happens if we timeout, do we still unregister?? */