USB: serial: mos7720: fix error code in mos7720_write()

This code should return -ENOMEM if the kmalloc() fails but instead
it returns success.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 0f64478c ("USB: add USB serial mos7720 driver")
Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/mos7720.c

@@ -1094,8 +1094,10 @@ static int mos7720_write(struct tty_struct *tty, struct usb_serial_port *port,
 	if (urb->transfer_buffer == NULL) {
 		urb->transfer_buffer = kmalloc(URB_TRANSFER_BUFFER_SIZE,
 					       GFP_ATOMIC);
-		if (!urb->transfer_buffer)
+		if (!urb->transfer_buffer) {
+			bytes_sent = -ENOMEM;
 			goto exit;
+		}
 	}
 	transfer_size = min(count, URB_TRANSFER_BUFFER_SIZE);