btrfs: use the btrfs_space_info_free_bytes_may_use helper for delalloc

We are going to use the ticket infrastructure for data, so use the
btrfs_space_info_free_bytes_may_use() helper in
btrfs_free_reserved_data_space_noquota() so we get the
btrfs_try_granting_tickets call when we free our reservation.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Tested-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>