sink/sourcewidget: Move the index and card_index to the devicewidget

This is a minor cleanup that moves the index of the sink/source and the
card_index from the sink/source widget to the device widget.

src/devicewidget.h

@@ -39,6 +39,7 @@ public:
 
     Glib::ustring name;
     Glib::ustring description;
+    uint32_t index, card_index;
 
     Gtk::ToggleButton *lockToggleButton, *muteToggleButton, *defaultToggleButton;
 

src/sinkwidget.h

@@ -41,7 +41,7 @@ public:
     static SinkWidget* create(MainWindow* mainWindow);
 
     SinkType type;
-    uint32_t index, monitor_index, card_index;
+    uint32_t monitor_index;
     bool can_decibel;
 
 #if HAVE_EXT_DEVICE_RESTORE_API

src/sourcewidget.h

@@ -31,7 +31,6 @@ public:
     static SourceWidget* create(MainWindow* mainWindow);
 
     SourceType type;
-    uint32_t index, card_index;
     bool can_decibel;
 
     virtual void onMuteToggleButton();