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/ls1021aqds_qspi_defconfig b/configs/ls1021aqds_qspi_defconfig
index 70013eb..8cd6024 100644
--- a/configs/ls1021aqds_qspi_defconfig
+++ b/configs/ls1021aqds_qspi_defconfig
@@ -38,9 +38,9 @@
 CONFIG_FSL_ESDHC=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_SPANSION=y
-CONFIG_NETDEVICES=y
 CONFIG_PHY_GIGE=y
 CONFIG_E1000=y
+CONFIG_MII=y
 CONFIG_TSEC_ENET=y
 CONFIG_PCI=y
 CONFIG_DM_PCI=y