Direct2D QPA config test: Test for presence of IDXGISurface1

Partial Direct2D was added to recent versions of MinGW, which made the
config test pass but is not sufficient to actually build the plugin.
Check for IDXGISurface1 in addition.

Change-Id: Ie108f5735ceb0a44934429b0fd2213612ed28848
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

config.tests/qpa/direct2d/direct2d.cpp

@@ -50,6 +50,8 @@ int main(int, char**)
 {
     ComPtr<ID2D1Factory1> d2dFactory;
     D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, d2dFactory.ReleaseAndGetAddressOf());
+    ComPtr<IDXGISurface1> surface;
+    (void)surface; // Q_UNUSED
 
     return 0;
 }