USB: serial: ch341: fix type promotion bug in ch341_control_in()

The "r" variable is an int and "bufsize" is an unsigned int so the
comparison is type promoted to unsigned. If usb_control_msg() returns a
negative that is treated as a high positive value and the error handling
doesn't work.

Fixes: 2d5a9c72d0c4 ("USB: serial: ch341: fix control-message error handling")
Signed-off-by: Dan Carpenter <[e-mail]>
Cc: stable <[e-mail]>
Signed-off-by: Johan Hovold <[e-mail]>

drivers/usb/serial/ch341.c

···
 	r = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), request,
 			    USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
 			    value, index, buf, bufsize, DEFAULT_TIMEOUT);
-	if (r < bufsize) {
+	if (r < (int)bufsize) {
 		if (r >= 0) {
 			dev_err(&dev->dev,
 				"short control message received (%d < %u)\n",