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/M5475GFE_defconfig b/configs/M5475GFE_defconfig
index ee7793c..39d3409 100644
--- a/configs/M5475GFE_defconfig
+++ b/configs/M5475GFE_defconfig
@@ -15,6 +15,7 @@
 CONFIG_CMD_PING=y
 CONFIG_CMD_CACHE=y
 CONFIG_MTD_NOR_FLASH=y
+CONFIG_MII=y
 CONFIG_PCI=y
 CONFIG_USB=y
 CONFIG_USB_STORAGE=y