dbus: prefer expat if available even if libxml2 also is

dbus-glib needs dbus to be compiled with expat support, so prefer that
mode even if libxml2 is also enabled.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/dbus/Config.in

@@ -12,7 +12,7 @@ comment "dbus not available (need expat or libxml2)"
 choice
 	prompt "XML library to use"
 	depends on BR2_PACKAGE_DBUS
-	default BR2_DBUS_LIBXML2 if BR2_PACKAGE_LIBXML2
+	default BR2_DBUS_LIBXML2 if (BR2_PACKAGE_LIBXML2 && !BR2_PACKAGE_EXPAT)
 	default BR2_DBUS_EXPAT
 	help
 	  Select the XML library to use with D-Bus. Select Expat