LU-6142 obdclass: change some foo0() to __foo()

LU-6142 obdclass: change some foo0() to __foo()

Change:
  cl_io_init0 -> __cl_io_init
  cl_lock_trace0 -> __cl_lock_trace
  cl_page_delete0 -> __cl_page_delete
  cl_page_state_set0 -> __cl_page_state_set
  cl_page_own0 -> __cl_page_own
  cl_page_disown0 -> __cl_page_disown
  cl_page_delete0 -> __cl_page_delete

This is more consistent with Linux naming style.

Test-Parameters: trivial
Change-Id: If38b52465d42ac425d47c1e9ded62bd7f013e0eb
Signed-off-by: Mr. NeilBrown <neilb@suse.de>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/48803
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>