LU-8066 llite: move /proc/fs/lustre/llite/statahead_{max, agl} to sysfs

LU-8066 llite: move /proc/fs/lustre/llite/statahead_{max, agl} to sysfs

Move statahead_max and statahead_agl files from /proc/fs/lustre/llite/*
to /sys/fs/lustre/llite/*/

This is a modified version of

Linux-commit: 4081a3201ade8b3be715ebb0b7879a2bfe5fcc98

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

Change-Id: Ic16d48d0cf1baabb462952de9739544923eba8cd
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/32504
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>