LU-8066 llite: don't use class_setup_tunables()

LU-8066 llite: don't use class_setup_tunables()

llite is very different from the other types of lustre devices.
Since this is the case llite should register independently. Doing
this allows us to cleanup the debugfs registering in the release
function of struct kobj_type. Also fix the improper handling to
linking it to the lustre_kset. Use kset_get() and kset_put() to
properly keep the reference count for the lustre_kset. This
lastly provides flexibility for making changes to
class_setup_tunables().

Change-Id: I676159caa7885485fdd57c908123214f68514227
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/34292
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>