Changed PPC4xx EMAC driver to require CONFIG_PPC4xx_EMAC

All in-tree IBM/AMCC PPC4xx boards using the EMAC get this new CONFIG

Signed-off-by: Ben Warren <biggerbadderben@gmail.com>
Acked-by: Stefan Roese <sr@denx.de>
diff --git a/include/configs/PIP405.h b/include/configs/PIP405.h
index 2966979..5c4d69b 100644
--- a/include/configs/PIP405.h
+++ b/include/configs/PIP405.h
@@ -278,6 +278,7 @@
 /************************************************************
  * Ethernet Stuff
  ***********************************************************/
+#define CONFIG_PPC4xx_EMAC
 #define CONFIG_MII		1	/* MII PHY management		*/
 #define CONFIG_PHY_ADDR		1	/* PHY address			*/
 /************************************************************