LU-6142 obdclass: resolve lu_ref checkpatch issues

LU-6142 obdclass: resolve lu_ref checkpatch issues

Fix up all the checkpatch issues reported for the code handling
lu_ref. Also change USE_LU_REF to CONFIG_LUSTRE_DEBUG_LU_REF
which will match what will be upstream.

Lustre-change: https://review.whamcloud.com/44088
Lustre-commit: 5c98de856618f301035c7579e61fffa10cc726cc

Change-Id: I100e2679fc04c97eb67e4d44c4f6a6b530da6fa8
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/51173
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>