rtw89: coex: correct C2H header length

To resolve C2H handle length mismatch, or it will parse the c2h content
out of array.
Signed-off-by: Ching-Te Ku <ku920601@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20211209083229.10815-2-pkshih@realtek.com

drivers/net/wireless/realtek/rtw89/coex.c

@@ -4494,6 +4494,8 @@ void rtw89_btc_c2h_handle(struct rtw89_dev *rtwdev, struct sk_buff *skb,
 	struct rtw89_btc_btf_fwinfo *pfwinfo = &btc->fwinfo;
 	u8 *buf = &skb->data[RTW89_C2H_HEADER_LEN];
 
+	len -= RTW89_C2H_HEADER_LEN;
+
 	rtw89_debug(rtwdev, RTW89_DBG_BTC,
 		    "[BTC], %s(): C2H BT len:%d class:%d fun:%d\n",
 		    __func__, len, class, func);