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/icnova-a20-swac_defconfig b/configs/icnova-a20-swac_defconfig
index 71c9288..cadd967 100644
--- a/configs/icnova-a20-swac_defconfig
+++ b/configs/icnova-a20-swac_defconfig
@@ -20,6 +20,7 @@
 # CONFIG_SPL_DOS_PARTITION is not set
 # CONFIG_SPL_EFI_PARTITION is not set
 CONFIG_ETH_DESIGNWARE=y
+CONFIG_MII=y
 CONFIG_SUN7I_GMAC=y
 CONFIG_USB_EHCI_HCD=y
 CONFIG_SYS_USB_EVENT_POLL_VIA_INT_QUEUE=y