usb: usbtmc: uninitialized symbol 'actual' in usbtmc_read

Fix uninitialized symbol 'actual' in function usbtmc_read.

When symbol 'actual' is not initialized and usb_bulk_msg() fails,
the subsequent kernel debug message shows a random value.
Signed-off-by: Guido Kiener <guido.kiener@rohde-schwarz.com>
Fixes: d7604ff0 ("usb: usbtmc: Optimize usbtmc_read")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/usbtmc.c

@@ -1370,6 +1370,7 @@ static ssize_t usbtmc_read(struct file *filp, char __user *buf,
 
 	/* Loop until we have fetched everything we requested */
 	remaining = count;
+	actual = 0;
 
 	/* Send bulk URB */
 	retval = usb_bulk_msg(data->usb_dev,