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/net/eth.c b/net/eth.c
index 0b954ed..eab5104 100644
--- a/net/eth.c
+++ b/net/eth.c
@@ -153,7 +153,7 @@
 #if defined(CONFIG_DB64460) || defined(CONFIG_P3Mx)
 	mv6446x_eth_initialize(bis);
 #endif
-#if defined(CONFIG_4xx) && !defined(CONFIG_IOP480) && !defined(CONFIG_AP1000)
+#if defined(CONFIG_PPC4xx_EMAC)
 	ppc_4xx_eth_initialize(bis);
 #endif
 	if (!eth_devices) {
@@ -485,8 +485,7 @@
 #if defined(CONFIG_AT91RM9200)
 	at91rm9200_miiphy_initialize(bis);
 #endif
-#if defined(CONFIG_4xx) && !defined(CONFIG_IOP480) \
-	&& !defined(CONFIG_AP1000) && !defined(CONFIG_405)
+#if defined(CONFIG_PPC4xx_EMAC)
 	emac4xx_miiphy_initialize(bis);
 #endif
 #if defined(CONFIG_MCF52x2)