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/W7OLMG.h b/include/configs/W7OLMG.h
index 2260338..ca1a9d4 100644
--- a/include/configs/W7OLMG.h
+++ b/include/configs/W7OLMG.h
@@ -65,6 +65,7 @@
 #define CONFIG_LOADS_ECHO	1		/* echo on for serial download	*/
 #undef CONFIG_SYS_LOADS_BAUD_CHANGE			/* disallow baudrate change	*/
 
+#define CONFIG_PPC4xx_EMAC
 #define CONFIG_MII		1		/* MII PHY management		*/
 #define CONFIG_PHY_ADDR		0		/* PHY address			*/