tests: Add usage to init of VkDepthStencilObj

Change-Id: Ia99032354e34b87ac200fccb0c69a420cc1d448d
diff --git a/tests/vkrenderframework.h b/tests/vkrenderframework.h
index 1a802df..336d0e6 100644
--- a/tests/vkrenderframework.h
+++ b/tests/vkrenderframework.h
@@ -343,7 +343,7 @@
   public:
     VkDepthStencilObj(VkDeviceObj *device);
     void Init(VkDeviceObj *device, int32_t width, int32_t height,
-                       VkFormat format);
+                       VkFormat format, VkImageUsageFlags usage = VK_IMAGE_USAGE_DEPTH_STENCIL_ATTACHMENT_BIT);
     bool Initialized();
     VkImageView *BindInfo();
 
@@ -453,5 +453,4 @@
     vector<VkPipelineColorBlendAttachmentState> m_colorAttachments;
     int m_vertexBufferCount;
 };
-
 #endif // VKRENDERFRAMEWORK_H