LU-13344 all: Separate debugfs and procfs handling

LU-13344 all: Separate debugfs and procfs handling

Linux 5.6 introduces proc_ops with v5.5-8862-gd56c0d45f0e2
proc: decouple proc from VFS with "struct proc_ops"

Separate debugfs usage and procfs usage to prepare for the divergence
of debugfs using file_operations and procfs using proc_ops

Lustre-change: https://review.whamcloud.com/37834
Lustre-commit: 76626d6c52b19b5cca04007c4b1656cc52a487c1

HPE-bug-id: LUS-8589
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I1746e563b55a9e89f90ac01843c304fe6b690d8b
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/43641
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Li Xi <lixi@ddn.com>