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/sbc8548_PCI_66_defconfig b/configs/sbc8548_PCI_66_defconfig
index 9d86d0c..46d41f1 100644
--- a/configs/sbc8548_PCI_66_defconfig
+++ b/configs/sbc8548_PCI_66_defconfig
@@ -21,7 +21,7 @@
 # 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_OF_LIBFDT=y