radv/rt: Free traversal NIR after compilation

Could lead to OOM in games that compile RTPSOs often,
like Ghostwire Tokyo.

Cc: mesa-stable
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26892>
(cherry picked from commit 34cc765172)

.pick_status.json

@@ -14,7 +14,7 @@
         "description": "radv/rt: Free traversal NIR after compilation",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": null,
         "notes": null

src/amd/vulkan/radv_pipeline_rt.c

@@ -609,6 +609,7 @@ radv_rt_compile_shaders(struct radv_device *device, struct vk_pipeline_cache *ca
    radv_shader_layout_init(pipeline_layout, MESA_SHADER_INTERSECTION, &traversal_stage.layout);
    result = radv_rt_nir_to_asm(device, cache, pCreateInfo, key, pipeline, false, &traversal_stage, NULL, NULL,
                                &pipeline->base.base.shaders[MESA_SHADER_INTERSECTION]);
+   ralloc_free(traversal_module.nir);
 
 cleanup:
    for (uint32_t i = 0; i < pCreateInfo->stageCount; i++)