LU-9859 libcfs: hide struct cfs_cpt_table internals

Exposing the internals of struct cfs_cpt_table in the libcfs
header used by lustre makes it too tempting to use but those
fields are not available for UP systems. Make cfs_cpt_table
abstract so the lustre and LNet code will never use the
internals and instead use the functions provided in
libcfs_cpu.h.

Linux-commit: commit a6fe6f584b6a1032c2e63e94d7a7a6f1436c3774

Change-Id: Ia2b3363bcee87e042a133cc7af9a912cbafb0d92
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/38389
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Oleg Drokin <green@whamcloud.com>