SpinBox: Enable hover in mouse up and down areas

Otherwise the properties upHovered and downHovered can never be true.

Change-Id: If8bb93961efa740028ace484099f3a6ce20e168e
Reviewed-by: Mitch Curtis <mitch.curtis@digia.com>

src/qtdesktop/SpinBox.qml

@@ -167,6 +167,7 @@ FocusScope {
 
     MouseArea {
         id: mouseUp
+        hoverEnabled: true
 
         property var upRect: loader.item  ?  loader.item.upRect : null
 
@@ -191,6 +192,8 @@ FocusScope {
 
     MouseArea {
         id: mouseDown
+        hoverEnabled: true
+
         onClicked: decrement()
         property var downRect: loader.item ? loader.item.downRect : null