staging: erofs: rearrange vle clustertype definitions

This patch moves vle clustertype definitions to erofs_fs.h
since they are part of on-disk format.

It also adds compile time check for Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS

Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>