ath5k: use rx hw descriptor pointer for self-linked check

This patch simplifies the code used to detect when the
self-linked DMA buffer is still in use by hardware, by
checking the hardware's rxdp register instead of looking
at the software buffer list.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
Acked-by: Nick Kossifidis <mickflemm@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath5k/base.h

@@ -56,7 +56,6 @@
 
 struct ath5k_buf {
 	struct list_head	list;
-	unsigned int		flags;	/* rx descriptor flags */
 	struct ath5k_desc	*desc;	/* virtual addr of desc */
 	dma_addr_t		daddr;	/* physical addr of desc */
 	struct sk_buff		*skb;	/* skbuff for buf */