btrfs: remove more obsolete v0 extent ref declarations

The extent references v0 have been superseded long time go, there are
some unused declarations of access helpers. We can safely remove them
now. The struct btrfs_extent_ref_v0 is not used anywhere, but struct
btrfs_extent_item_v0 is still part of a backward compatibility check in
relocation.c and thus not removed.
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -1648,9 +1648,6 @@ BTRFS_SETGET_FUNCS(extent_generation, struct btrfs_extent_item,
 		   generation, 64);
 BTRFS_SETGET_FUNCS(extent_flags, struct btrfs_extent_item, flags, 64);
 
-BTRFS_SETGET_FUNCS(extent_refs_v0, struct btrfs_extent_item_v0, refs, 32);
-
-
 BTRFS_SETGET_FUNCS(tree_block_level, struct btrfs_tree_block_info, level, 8);
 
 static inline void btrfs_tree_block_key(struct extent_buffer *eb,
@@ -1698,12 +1695,6 @@ static inline u32 btrfs_extent_inline_ref_size(int type)
 	return 0;
 }
 
-BTRFS_SETGET_FUNCS(ref_root_v0, struct btrfs_extent_ref_v0, root, 64);
-BTRFS_SETGET_FUNCS(ref_generation_v0, struct btrfs_extent_ref_v0,
-		   generation, 64);
-BTRFS_SETGET_FUNCS(ref_objectid_v0, struct btrfs_extent_ref_v0, objectid, 64);
-BTRFS_SETGET_FUNCS(ref_count_v0, struct btrfs_extent_ref_v0, count, 32);
-
 /* struct btrfs_node */
 BTRFS_SETGET_FUNCS(key_blockptr, struct btrfs_key_ptr, blockptr, 64);
 BTRFS_SETGET_FUNCS(key_generation, struct btrfs_key_ptr, generation, 64);

include/uapi/linux/btrfs_tree.h

@@ -519,15 +519,6 @@ struct btrfs_extent_inline_ref {
 	__le64 offset;
 } __attribute__ ((__packed__));
 
-/* old style backrefs item */
-struct btrfs_extent_ref_v0 {
-	__le64 root;
-	__le64 generation;
-	__le64 objectid;
-	__le32 count;
-} __attribute__ ((__packed__));
-
-
 /* dev extents record free space on individual devices.  The owner
  * field points back to the chunk allocation mapping tree that allocated
  * the extent.  The chunk tree uuid field is a way to double check the owner