anv: Start to move anv_gem_stubs.c to kmd backend

Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20948>

src/intel/vulkan/tests/state_pool_padding.c

@@ -31,6 +31,7 @@ int main(void)
    struct anv_state_pool state_pool;
 
    anv_device_set_physical(&device, &physical_device);
+   device.kmd_backend = anv_kmd_backend_get(INTEL_KMD_TYPE_STUB);
    pthread_mutex_init(&device.mutex, NULL);
    anv_bo_cache_init(&device.bo_cache, &device);
    anv_state_pool_init(&state_pool, &device, "test", 4096, 0, 4096);