ixp: move serial to drivers/serial

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/include/configs/actux4.h b/include/configs/actux4.h
index f2b701f..cdc9956 100644
--- a/include/configs/actux4.h
+++ b/include/configs/actux4.h
@@ -32,6 +32,7 @@
 #define CONFIG_DISPLAY_CPUINFO		1
 #define CONFIG_DISPLAY_BOARDINFO	1
 
+#define CONFIG_IXP_SERIAL
 #define CONFIG_SYS_IXP425_CONSOLE		IXP425_UART1
 #define CONFIG_BAUDRATE			115200
 #define CONFIG_BOOTDELAY		3