The 'refcount_bits' term used in the description of refcount block entry is
not defined in the specification. The definition is added in the
'refcount_order' section where refcount_bits was used as 'width in bits'.
Signed-off-by: Maria Kustova <maria.k@catit.be>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>