Fix build without highdpiscaling feature

Fixes: QTBUG-104925
Pick-to: 6.4
Change-Id: Ieb5dd2194c54a61733c427c8a0ddf7576147d6ea
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/gui/kernel/qhighdpiscaling_p.h

@@ -343,6 +343,9 @@ public:
 };
 
 namespace QHighDpi {
+    template <typename T> inline
+    T scale(const T &value, ...) { return value; }
+
     template <typename T> inline
     T toNative(const T &value, ...) { return value; }
     template <typename T> inline