f2fs: cleanup the code in build_sit_entries.

We do not need to set the SBI_NEED_FSCK flag in the error paths, if we
return error here, we will not update the checkpoint flag, so the code
is useless, just remove it.

Signed-off-by: Lihong Kou <koulihong@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>