ocfs2: correctly use ocfs2_find_next_zero_bit()

If no bits are zero, ocfs2_find_next_zero_bit() will return max size, so
check the return value with -1 is meaningless.  Correct this usage and
cleanup the code.

Link: https://lkml.kernel.org/r/20240314021713.240796-1-joseph.qi@linux.alibaba.com
Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: Heming Zhao <heming.zhao@suse.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.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>