MIPS: kernel: cevt-r4k: Add MIPS R6 to the c0_compare_interrupt handler

Just like MIPS R2, in MIPS R6 it is possible to determine if a
timer interrupt has happened or not.
Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

arch/mips/kernel/cevt-r4k.c

@@ -39,7 +39,7 @@ int cp0_timer_irq_installed;
 
 irqreturn_t c0_compare_interrupt(int irq, void *dev_id)
 {
-	const int r2 = cpu_has_mips_r2;
+	const int r2 = cpu_has_mips_r2_r6;
 	struct clock_event_device *cd;
 	int cpu = smp_processor_id();