microblaze: Fix level interrupt ACKing

Level interrupts need to be ack'd in the unmask handler, as in powerpc.
Among other issues, this bug causes the system clock to appear to run at
double-speed.

Signed-off-by: Steven J. Magnani <steve@digidescorp.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/kernel/intc.c

@@ -42,8 +42,16 @@ unsigned int nr_irq;
 
 static void intc_enable_or_unmask(unsigned int irq)
 {
+	unsigned long mask = 1 << irq;
 	pr_debug("enable_or_unmask: %d\n", irq);
-	out_be32(INTC_BASE + SIE, 1 << irq);
+	out_be32(INTC_BASE + SIE, mask);
+
+	/* ack level irqs because they can't be acked during
+	 * ack function since the handle_level_irq function
+	 * acks the irq before calling the interrupt handler
+	 */
+	if (irq_desc[irq].status & IRQ_LEVEL)
+		out_be32(INTC_BASE + IAR, mask);
 }
 
 static void intc_disable_or_mask(unsigned int irq)