LU-16518 obd: fix style and clang error

LU-16518 obd: fix style and clang error

Tabify the remaining code in this file and clean
up some of the comments. Add SPDX text.

Remove a function which is never used.

Fix the style of and inline cl_io_invariant.

Conserve a significant number of * so that they
can be repurposed in other comments.

Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: I6b1c5c700d7e6f13c8c57726db5da6595b9c060a
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51311
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Oleg Drokin <green@whamcloud.com>