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/mgcoge3un_defconfig b/configs/mgcoge3un_defconfig
index baee230..6c974b3 100644
--- a/configs/mgcoge3un_defconfig
+++ b/configs/mgcoge3un_defconfig
@@ -33,8 +33,8 @@
 # CONFIG_MMC is not set
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_STMICRO=y
-CONFIG_NETDEVICES=y
 CONFIG_MVGBE=y
+CONFIG_MII=y
 CONFIG_SYS_NS16550=y
 CONFIG_SPI=y
 CONFIG_KIRKWOOD_SPI=y