ixp4xx: allocate all skbs using GFP_DMA this ensures that dma bounce buffers will not be used frequently when bridging or routing frames between ethernet and wifi. significantly improves ath9k performance and obsoletes an ath specific patch

SVN-Revision: 19051

target/linux/ixp4xx/patches-2.6.30/600-dma_performance.patch

@@ -0,0 +1,13 @@
+--- a/net/core/skbuff.c
++++ b/net/core/skbuff.c
+@@ -260,6 +260,10 @@ struct sk_buff *__alloc_skb(unsigned int
+ 	if (!skb)
+ 		goto out;
+ 
++#ifdef CONFIG_ARCH_IXP4XX
++	gfp_mask |= GFP_DMA;
++#endif
++
+ 	size = SKB_DATA_ALIGN(size);
+ 	data = kmalloc_node_track_caller(size + sizeof(struct skb_shared_info),
+ 			gfp_mask, node);