InputCommon: Use value of "Modifier" button "Range" setting rather than always applying 50%.

Make "Clear" button reset "Modifier" "Range" settings to 50%.

Source/Core/InputCommon/ControllerEmu/ControlGroup/AnalogStick.h

@@ -23,6 +23,8 @@ public:
   StateData GetState() const;
 
 private:
+  Control* GetModifierInput() const override;
+
   std::unique_ptr<StickGate> m_stick_gate;
 };