That is, don't just flush it, but unmap it as well.

As of d8e8ab21, we can get here even when
!wined3d_map_persistent(). Thus we currently end up leaving BOs mapped when
performing an accelerated DISCARD map. Try to avoid that.
Signed-off-by: Zebediah Figura <zfigura@codeweavers.com>
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>