USB: Fix usb_serial_driver structure for Kobil cardreader driver.

The device setup did miss to initialize the num_interrupt_out field, thus
failing to successfully complete the probe function.

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Cc: Alan Cox <alan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>