[MIPS] time: Fix negated condition in cevt-r4k driver.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/cevt-r4k.c

@@ -276,7 +276,7 @@ void __cpuinit mips_clockevent_init(void)
 
 	clockevents_register_device(cd);
 
-	if (!cp0_timer_irq_installed)
+	if (cp0_timer_irq_installed)
 		return;
 
 	cp0_timer_irq_installed = 1;