ath9k: fix invalid pointer access in the tx path

After setup_frame_info has been called, only info->control.rates is still
valid, other control fields have been overwritten by the ath_frame_info
data. Move the access to info->control.vif for checking short preamble
to setup_frame_info before it gets overwritten.

This regression was introduced in commit d47a61aa
"ath9k: Fix multi-VIF BSS handling"

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Reported-by: Thomas Hühn <thomas@net.t-labs.tu-berlin.de>
Acked-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Cc: stable@vger.kernel.org [3.4]
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 a277cf6..4866550 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -214,6 +214,7 @@
 	enum ath9k_key_type keytype;
 	u8 keyix;
 	u8 retries;
+	u8 rtscts_rate;
 };
 
 struct ath_buf_state {