[kcm] Fix layouting issues

The DeviceListItem's content was sometimes lacking proper padding to the
right, caused by internal layouting issues.

src/kcm/package/contents/ui/DeviceListItem.qml

@@ -39,15 +39,11 @@ ColumnLayout {
 
     RowLayout {
         spacing: Kirigami.Units.smallSpacing
-        Layout.minimumHeight: portbox.implicitHeight
+        Layout.fillWidth: true
 
         RadioButton {
             id: defaultButton
-            // Maximum width of the button need to match the text. Empty area must not change the default device.
-            Layout.maximumWidth: delegate.width - Layout.leftMargin - Layout.rightMargin
-                                    - (portbox.visible ? Kirigami.Units.gridUnit + portLabel.implicitWidth + Kirigami.Units.smallSpacing + portbox.implicitWidth : 0)
-                                    - balanceButton.width
-            // Margins and spacing are set to center RadioButton with muteButton, and text with VolumeSlider.
+            Layout.fillWidth: true
             Layout.leftMargin: LayoutMirroring.enabled ? 0 : Math.round((muteButton.width - defaultButton.indicator.width) / 2)
             Layout.rightMargin: LayoutMirroring.enabled ? Math.round((muteButton.width - defaultButton.indicator.width) / 2) : 0
             spacing: Kirigami.Units.smallSpacing + Math.round((muteButton.width - defaultButton.indicator.width) / 2)
@@ -59,18 +55,12 @@ ColumnLayout {
 
         Label {
             id: soloLabel
-            Layout.maximumWidth: delegate.width
-                                    - (portbox.visible ? Kirigami.Units.gridUnit + portLabel.implicitWidth + Kirigami.Units.smallSpacing + portbox.implicitWidth : 0)
-                                    - balanceButton.width
+            Layout.fillWidth: true
             text: defaultButton.text
             visible: delegate.ListView.view.count <= 1
             elide: Text.ElideRight
         }
 
-        Item {
-            Layout.fillWidth: true
-        }
-
         Label {
             id: portLabel
             visible: portbox.visible