iris: Change keybox parenting

For temporary lookups, just allocate out of the NULL ralloc context,
so we don't have to edit the linked list of ralloc children to add it
and then immediately remove it again.

When uploading a new shader, allocate the keybox off the shader, so
if we delete the shader the keybox also goes away.  Less manual cleanup.

src/gallium/drivers/iris/iris_program_cache.c

@@ -89,8 +89,7 @@ iris_find_cached_shader(struct iris_context *ice,
                         uint32_t key_size,
                         const void *key)
 {
-   struct keybox *keybox =
-      make_keybox(ice->shaders.cache, cache_id, key, key_size);
+   struct keybox *keybox = make_keybox(NULL, cache_id, key, key_size);
    struct hash_entry *entry =
       _mesa_hash_table_search(ice->shaders.cache, keybox);
 
@@ -191,7 +190,7 @@ iris_upload_shader(struct iris_context *ice,
    /* Store the 3DSTATE shader packets and other derived state. */
    ice->vtbl.store_derived_program_state(ice, cache_id, shader);
 
-   struct keybox *keybox = make_keybox(cache, cache_id, key, key_size);
+   struct keybox *keybox = make_keybox(shader, cache_id, key, key_size);
    _mesa_hash_table_insert(ice->shaders.cache, keybox, shader);
 
    return shader;