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/gwventana_nand_defconfig b/configs/gwventana_nand_defconfig
index b82b04d..59bebc4 100644
--- a/configs/gwventana_nand_defconfig
+++ b/configs/gwventana_nand_defconfig
@@ -64,8 +64,8 @@
 CONFIG_NAND=y
 CONFIG_NAND_MXS=y
 CONFIG_PHYLIB=y
-CONFIG_NETDEVICES=y
 CONFIG_E1000=y
+CONFIG_MII=y
 CONFIG_PCI=y
 CONFIG_DM_SERIAL=y
 CONFIG_USB=y