btrfs: send: remove unused code

This code was first introduced in 31db9f7c23fb ("Btrfs: introduce
BTRFS_IOC_SEND for btrfs send/receive") and it was not functional, then
it got slightly refactored in e938c8ad543c ("Btrfs: code cleanups for
send/receive"), alas it was still dead. So let's remove it for good!

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/send.c

@@ -1271,12 +1271,6 @@ static int __iterate_backrefs(u64 ino, u64 offset, u64 root, void *ctx_)
 		 */
 		if (ino >= bctx->cur_objectid)
 			return 0;
-#if 0
-		if (ino > bctx->cur_objectid)
-			return 0;
-		if (offset + bctx->extent_len > bctx->cur_offset)
-			return 0;
-#endif
 	}
 
 	bctx->found++;