Staging: ipack/bridges/tpci200: fix the uninstall the ipack device

Using the call to the ipack_device_unregister() function to avoid the
strange way it was doing, as the device model will take care of calling
the bus's .remove function when a device is being unregistered.

Signed-off-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>