fs: btrfs: Cleanup the old implementation

This cleans up the now unneeded code from the old btrfs implementation.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Marek BehĂșn <marek.behun@nic.cz>
diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 8d76422..fc074c8 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -2,6 +2,6 @@
 #
 # 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
 
-obj-y := btrfs.o chunk-map.o compression.o ctree.o dev.o dir-item.o \
-	extent-io.o inode.o root.o subvolume.o crypto/hash.o disk-io.o \
+obj-y := btrfs.o compression.o ctree.o dev.o dir-item.o \
+	extent-io.o inode.o subvolume.o crypto/hash.o disk-io.o \
 	common/rbtree-utils.o extent-cache.o volumes.o root-tree.o