USB: usbtmc: remove unnecessary memory allocation

Inside usbtmc_ioctl_clear_out_halt()/usbtmc_ioctl_clear_in_halt(),
usb_clear_halt() needn't any buffer to pass in, so remove the
unnecessary memory allocation.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>