erofs: fix incorrect early exits in volume label handling

erofs: fix incorrect early exits in volume label handling

Crafted EROFS images containing valid volume labels can trigger
incorrect early returns, leading to folio reference leaks.

However, this does not cause system crashes or other severe issues.

Fixes: 1cf12c717741 ("erofs: Add support for FS_IOC_GETFSLABEL")
Cc: stable@kernel.org
Reviewed-by: Hongbo Li <lihongbo22@huawei.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>