ath9k: use a separate data structure for rx buffers

There's no shared code for handling both rx and tx buffers, and tx
buffers require a lot more metadata than rx buffers.
Using a separate data structure for rx reduces memory usage and improves
cache footprint.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index 8878f2d..83c0455 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -207,6 +207,14 @@
 	u8 baw_tracked : 1;
 };
 
+struct ath_rxbuf {
+	struct list_head list;
+	struct sk_buff *bf_mpdu;
+	void *bf_desc;
+	dma_addr_t bf_daddr;
+	dma_addr_t bf_buf_addr;
+};
+
 struct ath_buf_state {
 	u8 bf_type;
 	u8 bfs_paprd;
@@ -307,7 +315,7 @@
 	struct ath_descdma rxdma;
 	struct ath_rx_edma rx_edma[ATH9K_RX_QUEUE_MAX];
 
-	struct ath_buf *buf_hold;
+	struct ath_rxbuf *buf_hold;
 	struct sk_buff *frag;
 
 	u32 ampdu_ref;