btrfs: pass flags as unsigned long to btrfs_add_ordered_extent

The ordered_extent flags are declared as unsigned long, so pass them as
such to btrfs_add_ordered_extent.

Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Tested-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Boris Burkov <boris@bur.io>
[ hch: split from a larger patch ]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>