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/mx53ppd_defconfig b/configs/mx53ppd_defconfig
index 4143c03..bc7f64a 100644
--- a/configs/mx53ppd_defconfig
+++ b/configs/mx53ppd_defconfig
@@ -29,7 +29,7 @@
 CONFIG_SYS_BOOTCOUNT_EXT_DEVPART="0:5"
 CONFIG_SYS_BOOTCOUNT_ADDR=0x7000A000
 CONFIG_FSL_ESDHC=y
-CONFIG_NETDEVICES=y
+CONFIG_MII=y
 CONFIG_RTC_S35392A=y
 CONFIG_USB=y
 CONFIG_USB_STORAGE=y