brcm80211: fix possible memleak in brcmf_proto_msgbuf_attach

When brcmf_proto_msgbuf_attach fail and msgbuf->txflow_wq != NULL,
we should destroy the workqueue.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wang Yufen <wangyufen@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1595237765-66238-1-git-send-email-wangyufen@huawei.com

drivers/net/wireless/broadcom/brcm80211/brcmfmac/msgbuf.c

@@ -1620,6 +1620,8 @@ int brcmf_proto_msgbuf_attach(struct brcmf_pub *drvr)
 					  BRCMF_TX_IOCTL_MAX_MSG_SIZE,
 					  msgbuf->ioctbuf,
 					  msgbuf->ioctbuf_handle);
+		if (msgbuf->txflow_wq)
+			destroy_workqueue(msgbuf->txflow_wq);
 		kfree(msgbuf);
 	}
 	return -ENOMEM;