gnu: mate-panel: Add missing inputs for Wayland support.

* gnu/packages/mate.scm (mate-panel)[inputs]: Add gtk-layer-shell and
wayland.

gnu/packages/mate.scm

@@ -681,6 +681,7 @@ mate-volume-control, a MATE volume control application and applet.")
      `(("dconf" ,dconf)
        ("cairo" ,cairo)
        ("dbus-glib" ,dbus-glib)
+       ("gtk-layer-shell" ,gtk-layer-shell)
        ("gtk+" ,gtk+)
        ("libcanberra" ,libcanberra)
        ("libice" ,libice)
@@ -695,7 +696,8 @@ mate-volume-control, a MATE volume control application and applet.")
        ("mate-desktop" ,mate-desktop)
        ("mate-menus" ,mate-menus)
        ("pango" ,pango)
-       ("tzdata" ,tzdata)))
+       ("tzdata" ,tzdata)
+       ("wayland" ,wayland)))
     (home-page "https://mate-desktop.org/")
     (synopsis "Panel for MATE")
     (description