VideoConfig: Add SupportsPartialDepthCopies to backend info

D3D11 doesn't support partial copies of depth buffers via
CopySubResource(), so we need to use a different path for the EFB cache.

Source/Core/VideoBackends/Null/NullBackend.cpp

@@ -50,6 +50,8 @@ void VideoBackend::InitBackendInfo()
   g_Config.backend_info.bSupportsFramebufferFetch = false;
   g_Config.backend_info.bSupportsBackgroundCompiling = false;
   g_Config.backend_info.bSupportsLogicOp = false;
+  g_Config.backend_info.bSupportsLargePoints = false;
+  g_Config.backend_info.bSupportsPartialDepthCopies = false;
 
   // aamodes: We only support 1 sample, so no MSAA
   g_Config.backend_info.Adapters.clear();