[POWERPC] Fix irq radix tree remapping typo

The code for using the radix tree for reverse mapping of interrupts has
a typo that causes it to create incorrect mappings if the software and
hardware numbers happen to be different. This would, among others, cause
the IDE interrupt to fail on js20's. This fixes it.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/irq.c

@@ -693,7 +693,7 @@ unsigned int irq_radix_revmap(struct irq_host *host,
 	/* If not there, try to insert it */
 	virq = irq_find_mapping(host, hwirq);
 	if (virq != NO_IRQ)
-		radix_tree_insert(tree, virq, &irq_map[virq]);
+		radix_tree_insert(tree, hwirq, &irq_map[virq]);
  bail:
 	spin_unlock_irqrestore(&irq_big_lock, flags);
 	return virq;