powerpc: Fix irq_alloc_host() reference counting and callers

When I changed irq_alloc_host() to take an of_node
(52964f87c6: "Add an optional
device_node pointer to the irq_host"), I botched the reference
counting semantics.

Stephen pointed out that it's irq_alloc_host()'s business if
it needs to take an additional reference to the device_node,
the caller shouldn't need to care.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/cell/spider-pic.c

@@ -300,7 +300,7 @@ static void __init spider_init_one(struct device_node *of_node, int chip,
 		panic("spider_pic: can't map registers !");
 
 	/* Allocate a host */
-	pic->host = irq_alloc_host(of_node_get(of_node), IRQ_HOST_MAP_LINEAR,
+	pic->host = irq_alloc_host(of_node, IRQ_HOST_MAP_LINEAR,
 				   SPIDER_SRC_COUNT, &spider_host_ops,
 				   SPIDER_IRQ_INVALID);
 	if (pic->host == NULL)