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/tbs2910_defconfig b/configs/tbs2910_defconfig
index b193a4b..55cd9bd 100644
--- a/configs/tbs2910_defconfig
+++ b/configs/tbs2910_defconfig
@@ -41,6 +41,7 @@
 CONFIG_DWC_AHSATA=y
 CONFIG_FSL_ESDHC=y
 CONFIG_PHYLIB=y
+CONFIG_MII=y
 CONFIG_PCI=y
 CONFIG_DM_THERMAL=y
 CONFIG_USB=y