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/M5272C3_defconfig b/configs/M5272C3_defconfig
index 6f5ad07..7a4e1d4 100644
--- a/configs/M5272C3_defconfig
+++ b/configs/M5272C3_defconfig
@@ -14,3 +14,4 @@
 CONFIG_CMD_PING=y
 CONFIG_CMD_CACHE=y
 CONFIG_MTD_NOR_FLASH=y
+CONFIG_MII=y