libceph: define new ceph_file_layout structure

Define new ceph_file_layout structure and rename old ceph_file_layout
to ceph_file_layout_legacy. This is preparation for adding namespace
to ceph_file_layout structure.

Signed-off-by: Yan, Zheng <zyan@redhat.com>
diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index e7d38aa..75ecf96 100644
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -275,8 +275,8 @@
 
 struct ceph_pool_perm {
 	struct rb_node node;
-	u32 pool;
 	int perm;
+	s64 pool;
 };
 
 /*