ocfs2/cluster: neaten a member of o2net_msg_handler

ocfs2/cluster: neaten a member of o2net_msg_handler

It's odd that o2net_msg_handler::nh_func_data is declared as type
o2net_msg_handler_func*.  So neaten it.

Link: http://lkml.kernel.org/r/63ADC13FD55D6546B7DECE290D39E373F1F554DA@H3CMLB14-EX.srv.huawei-3com.com
Signed-off-by: Changwei Ge <ge.changwei@h3c.com>
Reviewed-by: Joseph Qi <jiangqi903@gmail.com>
Reviewed-by: Alex Chen <alex.chen@huawei.com>
Cc: Mark Fasheh <mfasheh@versity.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <ge.changwei@h3c.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>