ath9k: add support for the new rate control API

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 1915f12..8a1888d 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -234,6 +234,7 @@
 	dma_addr_t bf_daddr;		/* physical addr of desc */
 	dma_addr_t bf_buf_addr;	/* physical addr of data buffer, for DMA */
 	bool bf_stale;
+	struct ieee80211_tx_rate rates[4];
 	struct ath_buf_state bf_state;
 };