zink: disallow depth-stencil blits with format-change

The Vulkan spec says this about vkCmdBlitImage:

   "No format conversion is supported between depth/stencil images. The
    formats must match."

So yeah, let's stop trying to do this.

Reviewed-by: Dave Airlie <airlied@redhat.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3681>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3681>

src/gallium/drivers/zink/zink_blit.c

@@ -73,6 +73,10 @@ blit_native(struct zink_context *ctx, const struct pipe_blit_info *info)
        info->alpha_blend)
       return false;
 
+   if (util_format_is_depth_or_stencil(info->dst.format) &&
+       info->dst.format != info->src.format)
+      return false;
+
    struct zink_resource *src = zink_resource(info->src.resource);
    struct zink_resource *dst = zink_resource(info->dst.resource);