b43: Fix possible NULL pointer dereference in DMA code

Index: linux-2.6.25.6/drivers/net/wireless/b43/dma.c
===================================================================
@@ -847,12 +847,13 @@ struct b43_dmaring *b43_setup_dmaring(st
 	dma_addr_t dma_test;
 
 	ring = kzalloc(sizeof(*ring), GFP_KERNEL);
 	if (!ring)
 		goto out;
 	ring->type = type;
+	ring->dev = dev;
 
 	nr_slots = B43_RXRING_SLOTS;
 	if (for_tx)
 		nr_slots = B43_TXRING_SLOTS;
 
 	ring->meta = kcalloc(nr_slots, sizeof(struct b43_dmadesc_meta),

@@ -898,13 +899,12 @@ struct b43_dmaring *b43_setup_dmaring(st
 
 		dma_unmap_single(dev->dev->dma_dev,
 				 dma_test, b43_txhdr_size(dev),
 				 DMA_TO_DEVICE);
 	}
 
-	ring->dev = dev;
 	ring->nr_slots = nr_slots;
 	ring->mmio_base = b43_dmacontroller_base(type, controller_index);
 	ring->index = controller_index;
 	if (type == B43_DMA_64BIT)
 		ring->ops = &dma64_ops;
 	else