ocfs2: remove unused ocfs2_orphan_scan_exit() declaration

ocfs2: remove unused ocfs2_orphan_scan_exit() declaration

ocfs2_orphan_scan_exit() is declared but not implemented.  Also perform a
minor cleanup in ocfs2_link_credits()

Link: http://lkml.kernel.org/r/71604351584F6A4EBAE558C676F37CA4014FC208AC@H3CMLB12-EX.srv.huawei-3com.com
Signed-off-by: guozhonghua <guozhonghua@h3c.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>