libceph: rename ceph_pg -> ceph_pg_v1

Rename the old version this type to distinguish it from the new version.

Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Alex Elder <elder@inktank.com>
diff --git a/include/linux/ceph/rados.h b/include/linux/ceph/rados.h
index b65182a..e7cece6 100644
--- a/include/linux/ceph/rados.h
+++ b/include/linux/ceph/rados.h
@@ -64,7 +64,7 @@
  * placement group.
  * we encode this into one __le64.
  */
-struct ceph_pg {
+struct ceph_pg_v1 {
 	__le16 preferred; /* preferred primary osd */
 	__le16 ps;        /* placement seed */
 	__le32 pool;      /* object pool */
@@ -128,7 +128,7 @@
  * object layout - how a given object should be stored.
  */
 struct ceph_object_layout {
-	struct ceph_pg ol_pgid;   /* raw pg, with _full_ ps precision. */
+	struct ceph_pg_v1 ol_pgid;   /* raw pg, with _full_ ps precision. */
 	__le32 ol_stripe_unit;    /* for per-object parity, if any */
 } __attribute__ ((packed));