LU-13344 libcfs: Abstract proc_fs with proc_ops

LU-13344 libcfs: Abstract proc_fs with proc_ops

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

Map proc_ops and it's members to file_operations and
the appropriate members for older kernels.

One remaining 'PROC_OWNER()' macro is left to deal with
proc_ops being unable to sensibly map the owner member.

Lustre-change: https://review.whamcloud.com/37873
Lustre-commit: 13cd0f9f667c6e138a8cb235d4920f8b749cb154

Test-Parameters: trivial
HPE-bug-id: LUS-8589
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I3d8940a91b331c4f6bb31a9432194cc082c9cecd
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/43642
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>