Staging: ipack: Make ipack_device_register() analogous to device_register().

ipack_device_register() is no longer creating the struct ipack_device
but only registering it.  Instead of releasing memory directly the new
ipack_device->release callback is called.

This is preparational work for later patches.

Signed-off-by: Jens Taprogge <jens.taprogge@taprogge.org>
Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>