LU-8066 llite: Preparation to move /proc/fs/lustre/llite to sysfs

LU-8066 llite: Preparation to move /proc/fs/lustre/llite to sysfs

Add necessary infrastructure, add support for mountpoint
registration in /sys/fs/lustre/llite

This is a heavly modified version of

Linux-commit: fd0d04ba85f95169106701397417360541a983b3

due to the large amount of changes to the OpenSFS/Intel branch.

Change-Id: Ic9ca2044249a59dc79ebc86553c8b7ce7afbf710
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/24031
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>