Btrfs: TODO update

Signed-off-by: NChris Mason <chris.mason@oracle.com>

fs/btrfs/TODO

@@ -8,11 +8,8 @@
 * Add block mapping tree (simple dm layer)
 * Add simple tree locking (semaphore per tree)
 * Make allocator smarter
-* Only pin blocks allocated in this transaction
-* Add transaction handles
 * Do actual block accounting
 * Check compat and incompat flags on the inode
-* Port into the kernel
 * Add virtual filesystems, mountable snapshots
 * Get rid of struct ctree_path, limiting tree levels held at one time
 * Release