spirv2dxil: Only lower readonly images to SRVs when the option is set

This handles the case where readonly is explicitly marked in the shader,
rather than just inferred based on opt_access.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21913>

src/microsoft/spirv_to_dxil/dxil_spirv_nir.c

@@ -1085,7 +1085,8 @@ dxil_spirv_nir_passes(nir_shader *nir,
       } while (progress);
    }
 
-   NIR_PASS_V(nir, nir_lower_readonly_images_to_tex, true);
+   if (conf->read_only_images_as_srvs)
+      NIR_PASS_V(nir, nir_lower_readonly_images_to_tex, true);
    nir_lower_tex_options lower_tex_options = {
       .lower_txp = UINT32_MAX,
       .lower_invalid_implicit_lod = true,