Use DECLARE_FLEX_ARRAY() helper in drivers/net/wireless/ath/carl9170/wlan.h

[GustavoARSilva]

diff -u -p ./drivers/net/wireless/ath/carl9170/wlan.h /tmp/nothing/drivers/net/wireless/ath/carl9170/wlan.h
--- ./drivers/net/wireless/ath/carl9170/wlan.h
+++ /tmp/nothing/drivers/net/wireless/ath/carl9170/wlan.h
@@ -271,7 +271,6 @@ struct ar9170_tx_frame {

        union {
                struct ieee80211_hdr i3e;
-               u8 payload[0];
        } data;
 } __packed;