[applets/devicenotifier] Manually bind width of list item

Don't rely on the delegate to auto-size, as this is not reliable and can
cause a binding loop.

(cherry picked from commit 9494b433)

applets/devicenotifier/package/contents/ui/FullRepresentation.qml

@@ -134,6 +134,7 @@ PlasmaComponents3.Page {
             model: filterModel
 
             delegate: DeviceItem {
+                width: notifierDialog.width
                 udi: DataEngineSource
             }
             highlight: PlasmaComponents.Highlight { }