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/mx53ard_defconfig b/configs/mx53ard_defconfig
index 44cf61e..96c43e0 100644
--- a/configs/mx53ard_defconfig
+++ b/configs/mx53ard_defconfig
@@ -18,7 +18,7 @@
 CONFIG_FSL_ESDHC=y
 CONFIG_NAND=y
 CONFIG_NAND_MXC=y
-CONFIG_NETDEVICES=y
+CONFIG_MII=y
 CONFIG_SMC911X=y
 CONFIG_SMC911X_BASE=0xF4000000
 CONFIG_OF_LIBFDT=y