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/spear310_nand_defconfig b/configs/spear310_nand_defconfig
index 3610bc3..bf3361c 100644
--- a/configs/spear310_nand_defconfig
+++ b/configs/spear310_nand_defconfig
@@ -24,7 +24,7 @@
 CONFIG_MTD_DEVICE=y
 CONFIG_MTD_PARTITIONS=y
 CONFIG_NAND=y
-CONFIG_NETDEVICES=y
 CONFIG_PHY_GIGE=y
 CONFIG_ETH_DESIGNWARE=y
+CONFIG_MII=y
 CONFIG_CONS_INDEX=0