Properly sync queue before processing submission

* This isn't necessary if only one main queue is in use as FlushQ() syncs our
  main queue, but if the submission is on a separate compute family for example
  we need to sync it before processing any indirect readbacks.

renderdoc/driver/vulkan/wrappers/vk_queue_funcs.cpp

@@ -303,6 +303,8 @@ void WrappedVulkan::ReplayQueueSubmit(VkQueue queue, VkSubmitInfo2 submitInfo, r
     for(uint32_t c = 0; c < numCmds; c++)
     {
       DoSubmit(queue, submitInfo);
+      // ensure we wait for the submit to finish before processing it
+      ObjDisp(queue)->QueueWaitIdle(Unwrap(queue));
       FlushQ();
 
       ResourceId cmd = GetResID(submitInfo.pCommandBufferInfos[0].commandBuffer);