GPU: Reduce depth blits when not updated.

If the game initially clears the depth in a buffer, but then never uses
that depth again, don't keep blitting depth.

Improves #8538, by preventing the depth blits in this case.

GPU/Vulkan/FramebufferVulkan.cpp

@@ -412,6 +412,7 @@ void FramebufferManagerVulkan::BlitFramebufferDepth(VirtualFramebuffer *src, Vir
 	if (matchingDepthBuffer && matchingRenderSize && matchingSize) {
 		// TODO: Currently, this copies depth AND stencil, which is a problem.  See #9740.
 		draw_->CopyFramebufferImage(src->fbo, 0, 0, 0, 0, dst->fbo, 0, 0, 0, 0, src->renderWidth, src->renderHeight, 1, Draw::FB_DEPTH_BIT);
+		dst->last_frame_depth_updated = gpuStats.numFlips;
 	} else if (matchingDepthBuffer && matchingSize) {
 		/*
 		int w = std::min(src->renderWidth, dst->renderWidth);