ppc4xx: Add PPC405EX support

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/include/serial.h b/include/serial.h
index 30bfde3..e292f0c 100644
--- a/include/serial.h
+++ b/include/serial.h
@@ -22,8 +22,9 @@
 extern struct serial_device serial_scc_device;
 extern struct serial_device * default_serial_console (void);
 
-#if defined(CONFIG_405GP) || defined(CONFIG_405CR) || defined(CONFIG_440) \
-   || defined(CONFIG_405EP) || defined(CONFIG_405EZ) || defined(CONFIG_MPC5xxx)
+#if defined(CONFIG_405GP) || defined(CONFIG_405CR) || defined(CONFIG_440) || \
+    defined(CONFIG_405EP) || defined(CONFIG_405EZ) || defined(CONFIG_405EX) || \
+    defined(CONFIG_MPC5xxx)
 extern struct serial_device serial0_device;
 extern struct serial_device serial1_device;
 #if defined(CFG_NS16550_SERIAL)