eulerfs: remove redundant calculations

uniontech inclusion
category: cleanup
bugzilla: https://gitee.com/openeuler/kernel/issues/I4X47D?from=project-issue


CVE: NA

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The 'left' always is 0.
If it is not 0, it will 'goto out;' from the previous if judgment.

Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>