ath9k: use u8 for the tx key index

This saves some space in struct ath_frame_info

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 3a893e1..d961f11 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -207,8 +207,8 @@
 
 struct ath_frame_info {
 	int framelen;
-	u32 keyix;
 	enum ath9k_key_type keytype;
+	u8 keyix;
 	u8 retries;
 	u16 seqno;
 };