NFC: port100: Don't send a new command if one is still pending

This patch ensures that a command is not still in process before sending
a new one to the device. This can happen when neard is in constant
polling mode: the configure_hw command can be sent when neard restarts
polling after a LLCP SYMM timeout but before the device has returned in
timeout from the last DEP frame sent.
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/nfc/port100.c

@@ -809,6 +809,12 @@ static int port100_send_cmd_async(struct port100 *dev, u8 cmd_code,
 			PORT100_FRAME_MAX_PAYLOAD_LEN +
 			PORT100_FRAME_TAIL_LEN;
 
+	if (dev->cmd) {
+		nfc_err(&dev->interface->dev,
+			"A command is still in process\n");
+		return -EBUSY;
+	}
+
 	resp = alloc_skb(resp_len, GFP_KERNEL);
 	if (!resp)
 		return -ENOMEM;