nfc: s3fwrn5: replace the assertion with a WARN_ON

In s3fwrn5_fw_recv_frame, if fw_info->rsp is not empty, the
current code causes a crash via BUG_ON. However, s3fwrn5_fw_send_msg
does not crash in such a scenario. The patch replaces the BUG_ON
by returning the error to the callers and frees up skb.
Signed-off-by: Aditya Pakki <pakki001@umn.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/nfc/s3fwrn5/firmware.c

@@ -507,7 +507,10 @@ int s3fwrn5_fw_recv_frame(struct nci_dev *ndev, struct sk_buff *skb)
 	struct s3fwrn5_info *info = nci_get_drvdata(ndev);
 	struct s3fwrn5_fw_info *fw_info = &info->fw_info;
 
-	BUG_ON(fw_info->rsp);
+	if (WARN_ON(fw_info->rsp)) {
+		kfree_skb(skb);
+		return -EINVAL;
+	}
 
 	fw_info->rsp = skb;