ocfs2: make several functions and variables static (and some const)

ocfs2: make several functions and variables static (and some const)

There are a variety of functions and variables that are local to the
source and do not need to be in global scope, so make them static.  Also
make a couple of char arrays static const.

Cleans up sparse warnings:
  symbol 'o2hb_heartbeat_mode_desc' was not declared. Should it be static?
  symbol 'o2hb_heartbeat_mode' was not declared. Should it be static?
  symbol 'o2hb_dependent_users' was not declared. Should it be static?
  symbol 'o2hb_region_dec_user' was not declared. Should it be static?
  symbol 'o2nm_fence_method_desc' was not declared. Should it be static?
  symbol 'lockdep_keys' was not declared. Should it be static?

Link: http://lkml.kernel.org/r/20180628131659.12133-1-colin.king@canonical.com
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Cc: Mark Fasheh <mfasheh@versity.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <joseph.qi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>