sh: intc: Fix up build failure introduced by radix tree changes.

The radix tree retry logic got a bit of an overhaul and subsequently
broke the virtual IRQ subgroup build. Simply switch over to
radix_tree_deref_retry() as per the filemap changes, which the virq
lookup logic was modelled after in the first place.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

drivers/sh/intc/virq.c

@@ -215,7 +215,7 @@ restart:
 		entry = radix_tree_deref_slot((void **)entries[i]);
 		if (unlikely(!entry))
 			continue;
-		if (unlikely(entry == RADIX_TREE_RETRY))
+		if (radix_tree_deref_retry(entry))
 			goto restart;
 
 		irq = create_irq();