Btrfs: cleanup arguments to extent_clear_unlock_delalloc

This patch removes the io_tree argument for extent_clear_unlock_delalloc since
we always use &BTRFS_I(inode)->io_tree, and it separates out the extent tree
operations from the page operations.  This way we just pass in the extent bits
we want to clear and then pass in the operations we want done to the pages.
This is because I'm going to fix what extent bits we clear in some cases and
rather than add a bunch of new flags we'll just use the actual extent bits we
want to clear.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>