microblaze: Fix interrupt handler code

It is better to read ivr and react on it than do long parsing from
two regs. Interrupt controller returs actual irq number.

Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/cpu/interrupts.c

@@ -141,8 +141,8 @@ int interrupts_init (void)
 
 void interrupt_handler (void)
 {
-	int irqs = (intc->isr & intc->ier);	/* find active interrupt */
-	int i = 1;
+	int irqs = intc->ivr;	/* find active interrupt */
+	int mask = 1;
 #ifdef DEBUG_INT
 	int value;
 	printf ("INTC isr %x, ier %x, iar %x, mer %x\n", intc->isr, intc->ier,
@@ -150,9 +150,10 @@ void interrupt_handler (void)
 	R14(value);
 	printf ("Interrupt handler on %x line, r14 %x\n", irqs, value);
 #endif
-	struct irq_action *act = vecs;
-	while (irqs) {
-		if (irqs & 1) {
+	struct irq_action *act = vecs + irqs;
+
+	intc->iar = mask << irqs;
+
 #ifdef DEBUG_INT
 	printf
 	    ("Jumping to interrupt handler rutine addr %x,count %x,arg %x\n",
@@ -160,13 +161,6 @@ void interrupt_handler (void)
 #endif
 	act->handler (act->arg);
 	act->count++;
-			intc->iar = i;
-			return;
-		}
-		irqs >>= 1;
-		act++;
-		i <<= 1;
-	}
 
 #ifdef DEBUG_INT
 	printf ("Dump INTC reg, isr %x, ier %x, iar %x, mer %x\n", intc->isr,