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: I7ef5a4b1ee47827711a9d6654fda279abde06268
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/32722
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>