ocfs2: consolidate o2hb_global_hearbeat_mode_set() naming convention

s/o2hb_global_hearbeat_mode_set/o2hb_global_heartbeat_mode_set/ to make
the signature of those routines in a consistent manner with others for
heartbeating.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Acked-by: Sunil Mushran <sunil.mushran@gmail.com>
Cc: Gurudas Pai <gurudas.pai@oracle.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Noboru Iwamatsu <n_iwamatsu@jp.fujitsu.com>
Cc: Srinivas Eeeda <srinivas.eeda@oracle.com>
Cc: Tao Ma <tm@tao.ma>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>