usb: usbtmc: uninitialized symbol 'actual' in usbtmc_ioctl_abort_bulk_in_tag

Fix uninitialized symbol 'actual' in function
usbtmc_ioctl_abort_bulk_in_tag().

When symbol 'actual' is not initialized and usb_bulk_msg() fails,
the subsequent kernel debug message shows invalid data.

Signed-off-by: Guido Kiener <guido.kiener@rohde-schwarz.com>
Fixes: cbe743f1 ("usb: usbtmc: Fix ioctl USBTMC_IOCTL_ABORT_BULK_IN")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>