dbus-glib: workaround Kconfig issue with select

Kconfig gets confused about the selects and thinks there's a recursive
dependency around expat, so implement an alternative solution instead.

package/dbus-glib/Config.in

@@ -1,9 +1,12 @@
 config BR2_PACKAGE_DBUS_GLIB
 	bool "dbus-glib"
 	depends on BR2_PACKAGE_DBUS
+	depends on BR2_PACKAGE_EXPAT
 	select BR2_PACKAGE_LIBGLIB2
-	select BR2_PACKAGE_EXPAT
 	help
 	  GLib bindings for D-Bus.
 
 	  http://www.freedesktop.org/software/dbus
+
+comment "dbus-glib needs dbus to be compiled with expat support"
+	depends on !BR2_PACKAGE_EXPAT