LU-8066 llite: replace ll_process_config with class_modify_config

LU-8066 llite: replace ll_process_config with class_modify_config

The current method of handling tunables with ll_process_config can
not work with sysfs. So replace ll_process_config handling with
class_modify_config() which can handle sysfs, debugfs and procfs.

Change-Id: I40611930ab2b769c0661aa7dce0c7dd0f2d90204
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/32495
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Ben Evans <bevans@cray.com>