asahi: Don't allow linear depth/stencil buffers

We don't have a way to tell the ZLS hardware to use linear buffers, so if a buffer could be used for depth/stencil, we have to twiddle. This isn't a problem in practice, since depth/stencil buffers can't be shared across processes or mapped directly as linear.

Fixes faults in depthstencil-render-miplevels, which was picking linear for one buffer because of a STAGING bind flag. But that won't work :-)

Signed-off-by: Alyssa Rosenzweig alyssa@rosenzweig.io