btrfs: Fix wrong comment of btrfs_alloc_tree_block()
btrfs: Fix wrong comment of btrfs_alloc_tree_block()

These wrong comment was copyed from another function(expired) from
init, this patch fixed them.

Signed-off-by: Zhao Lei <aacdd228f50c574b28b524b23f12fb9d52d6e0e3@cn.fujitsu.com>
Signed-off-by: Chris Mason <e2e8c5702d8ed5f565988a1cf5bb35c9ce199e5e@fb.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs