pan/mdg: Set the z/s store intrinsic base correctly

When EXT_shader_framebuffer_fetch is used and only depth and/or
stencil are written, we can't rely on the first output being to
depth/stencil.

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5755>
1 file changed