radv: cache the slab bo pointer in the pipeline.

Otherwise each emission has to pointer chase across cachelines.

Reduces overhead seen with zink on pixmark volplosion test.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16393>

src/amd/vulkan/radv_pipeline.c

@@ -3810,6 +3810,8 @@ radv_upload_shaders(struct radv_device *device, struct radv_pipeline *pipeline,
    if (!pipeline->slab)
       return VK_ERROR_OUT_OF_DEVICE_MEMORY;
 
+   pipeline->slab_bo = pipeline->slab->alloc->arena->bo;
+
    /* Upload shader binaries. */
    uint64_t slab_va = radv_buffer_get_va(pipeline->slab->alloc->arena->bo);
    uint32_t slab_offset = pipeline->slab->alloc->offset;