mac80211: Fix insufficient headroom issue for AMSDU

ieee80211_amsdu_realloc_pad() fails to account for extra_tx_headroom,
the original reserved headroom might be eaten. Add the necessary
extra_tx_headroom.

Fixes: 6e0456b5 ("mac80211: add A-MSDU tx support")
Signed-off-by: Chih-Kang Chang <gary.chang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://lore.kernel.org/r/20210816085128.10931-2-pkshih@realtek.com
[fix indentation]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/tx.c

@@ -3242,7 +3242,9 @@ static bool ieee80211_amsdu_prepare_head(struct ieee80211_sub_if_data *sdata,
 	if (info->control.flags & IEEE80211_TX_CTRL_AMSDU)
 		return true;
 
-	if (!ieee80211_amsdu_realloc_pad(local, skb, sizeof(*amsdu_hdr)))
+	if (!ieee80211_amsdu_realloc_pad(local, skb,
+					 sizeof(*amsdu_hdr) +
+					 local->hw.extra_tx_headroom))
 		return false;
 
 	data = skb_push(skb, sizeof(*amsdu_hdr));