Convert CONFIG_MII et al to Kconfig

This converts the following to Kconfig:
   CONFIG_MII
   CONFIG_DRIVER_TI_EMAC

Signed-off-by: Adam Ford <aford173@gmail.com>
Acked-by: Jagan Teki <jagan@amarulasolutions.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/configs/MPC8641HPCN_defconfig b/configs/MPC8641HPCN_defconfig
index b3dd6ac..39db233 100644
--- a/configs/MPC8641HPCN_defconfig
+++ b/configs/MPC8641HPCN_defconfig
@@ -22,7 +22,7 @@
 # CONFIG_MMC is not set
 CONFIG_MTD_NOR_FLASH=y
 CONFIG_PHY_MARVELL=y
-CONFIG_NETDEVICES=y
+CONFIG_MII=y
 CONFIG_TSEC_ENET=y
 CONFIG_SYS_NS16550=y
 CONFIG_USB=y