staging: erofs: differentiate unsupported on-disk format

For some specific fields, use EOPNOTSUPP instead of EIO
for values which look sane but aren't supported right now.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190814103705.60698-2-gaoxiang25@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>