erofs: fix inode metadata space layout description in documentation

Xattrs, extents, data inline are _placed after_, not _followed by_ the
corresponding inode. This patch fixes it.

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20231010113915.436591-1-tiwei.btw@antgroup.com


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