xserver-xorg: select dbus

xserver-xorg had dbus in it's dependencies, but didn't select it in kconfig.

package/x11r7/xserver_xorg-server/Config.in

@@ -10,6 +10,7 @@ config BR2_PACKAGE_XSERVER_XORG_SERVER
 	select BR2_PACKAGE_XPROTO_GLPROTO
 	select BR2_PACKAGE_XPROTO_KBPROTO
 	select BR2_PACKAGE_XPROTO_RANDRPROTO
+	select BR2_PACKAGE_DBUS
 	select BR2_PACKAGE_FREETYPE
 	select BR2_PACKAGE_XLIB_LIBX11
 	select BR2_PACKAGE_XLIB_LIBXAU