[ofw] question on use of ib_put_mad

[Sean Hefty]

When must a user return all MADs to IBAL by calling ib_put_mad()?  The handle to
the mad pool is returned from get_spl_qp(), which makes me think that all mads
must be returned before calling destroy_qp().

Is this correct, and, if so, is it expected that the user will provide
synchronization to handle the case where callbacks occur while destroy_qp() is
being invoked?