USB: serial: ti_usb_3410_5052: fix control-message error handling

BugLink: http://bugs.launchpad.net/bugs/1691418

commit 39712e8b upstream.

Make sure to detect and return an error on zero-length control-message
transfers when reading from the device.

This addresses a potential failure to detect an empty transmit buffer
during close.

Also remove a redundant check for short transfer when sending a command.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

drivers/usb/serial/ti_usb_3410_5052.c

@@ -1352,13 +1352,10 @@ static int ti_command_out_sync(struct ti_device *tdev, __u8 command,
 		(USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT),
 		value, moduleid, data, size, 1000);
 
-	if (status == size)
-		status = 0;
-
-	if (status > 0)
-		status = -ECOMM;
+	if (status < 0)
+		return status;
 
-	return status;
+	return 0;
 }
 
 
@@ -1374,8 +1371,7 @@ static int ti_command_in_sync(struct ti_device *tdev, __u8 command,
 
 	if (status == size)
 		status = 0;
-
-	if (status > 0)
+	else if (status >= 0)
 		status = -ECOMM;
 
 	return status;