fix build error for win

modules/core/src/directx.cpp

@@ -1266,11 +1266,12 @@ void convertToD3D11Texture2D(InputArray src, ID3D11Texture2D* pD3D11Texture2D)
     if(!useCLNVEXT){
         __convertToD3D11Texture2DKHR(src,pD3D11Texture2D);
     }
+#ifdef HAVE_OPENCL_D3D11_NV
     else
     {
         __convertToD3D11Texture2DNV(src,pD3D11Texture2D);
     }
-
+#endif
 #endif
 }
 
@@ -1287,11 +1288,12 @@ void convertFromD3D11Texture2D(ID3D11Texture2D* pD3D11Texture2D, OutputArray dst
     if(!useCLNVEXT){
         __convertFromD3D11Texture2DKHR(pD3D11Texture2D,dst);
     }
+#ifdef HAVE_OPENCL_D3D11_NV
     else
     {
         __convertFromD3D11Texture2DNV(pD3D11Texture2D,dst);
     }
-
+#endif
 #endif
 }