asahi: add has_scratch to shader key

some stages are unspillable

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27616>

src/asahi/compiler/agx_compile.h

@@ -230,6 +230,9 @@ struct agx_shader_key {
    /* Library routines to link against */
    const nir_shader *libagx;
 
+   /* Whether scratch memory is available in the given shader stage */
+   bool has_scratch;
+
    union {
       struct agx_vs_shader_key vs;
       struct agx_fs_shader_key fs;

src/gallium/drivers/asahi/agx_state.c

@@ -1804,6 +1804,7 @@ agx_compile_nir(struct agx_device *dev, nir_shader *nir,
                                dev->params.num_clusters_total > 1) ||
                               dev->params.num_dies > 1;
    key.libagx = dev->libagx;
+   key.has_scratch = true;
 
    NIR_PASS(_, nir, agx_nir_lower_sysvals, true);
    NIR_PASS(_, nir, agx_nir_layout_uniforms, compiled, &key.reserved_preamble);