SystemUI: Show the icon of "Mobile data" and "Notification" in status bar

The DataTile and NotificationsTile set the state.iconId to be the
imageDrawable of the view, but the QSTileView use the state.icon,
so that the icon of "Mobile data" and "Notification" can't be shown.

Set the state.icon to be the imageDrawable of the view.

Change-Id: I0d38a999f6345486d70b6e8e2ab48ad6d442e2d0
CRs-Fixed: 808855