netarm: move serial driver to drivers/serial

add CONFIG_NETARM_SERIAL to activate the driver

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/include/configs/modnet50.h b/include/configs/modnet50.h
index b8ae018..74bab5f 100644
--- a/include/configs/modnet50.h
+++ b/include/configs/modnet50.h
@@ -56,6 +56,7 @@
 /*
  * select serial console configuration
  */
+#define CONFIG_NETARM_SERIAL
 #define CONFIG_SERIAL1		1	/* we use Serial line 1 */
 
 /* allow to overwrite serial and ethaddr */