kobject: convert ibmasm to use kref, not kobject

The IBM asm driver is using a kobject only for reference counting,
nothing else.  So switch it to use a kref instead, which is all that is
needed, and is much smaller.

Cc: Max Asböck <amax@us.ibm.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>