loader: Fix enumerate device layer properties

Loader was calling down the chain when is needs to
respond with aggregate data. This patch fixes
https://buganizer.corp.google.com/u/0/issues/26982782

Change-Id: I236183d5d781a6efc3d84db4a51376b8cc29664f
diff --git a/vulkan/libvulkan/loader.h b/vulkan/libvulkan/loader.h
index 8081c0e..a724411 100644
--- a/vulkan/libvulkan/loader.h
+++ b/vulkan/libvulkan/loader.h
@@ -94,6 +94,7 @@
 VKAPI_ATTR PFN_vkVoidFunction GetDeviceProcAddr_Top(VkDevice drv_device, const char* name);
 VKAPI_ATTR void GetDeviceQueue_Top(VkDevice drv_device, uint32_t family, uint32_t index, VkQueue* out_queue);
 VKAPI_ATTR VkResult AllocateCommandBuffers_Top(VkDevice device, const VkCommandBufferAllocateInfo* alloc_info, VkCommandBuffer* cmdbufs);
+VKAPI_ATTR VkResult EnumerateDeviceLayerProperties_Top(VkPhysicalDevice pdev, uint32_t* properties_count, VkLayerProperties* properties);
 VKAPI_ATTR VkResult CreateDevice_Top(VkPhysicalDevice pdev, const VkDeviceCreateInfo* create_info, const VkAllocationCallbacks* allocator, VkDevice* device_out);
 VKAPI_ATTR void DestroyDevice_Top(VkDevice drv_device, const VkAllocationCallbacks* allocator);