erofs: modify the error message when prepare_ondemand_read failed

When prepare_ondemand_read failed, wrong error message is printed.
The prepare_read is also implemented in cachefiles, so we amend it.

Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20240424084247.759432-1-lihongbo22@huawei.com


Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>