Convert CONFIG_MII_INIT to Kconfig

This converts the following to Kconfig:
   CONFIG_MII_INIT

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/MCR3000_defconfig b/configs/MCR3000_defconfig
index 04fe756..f174865 100644
--- a/configs/MCR3000_defconfig
+++ b/configs/MCR3000_defconfig
@@ -42,6 +42,7 @@
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_DHCP=y
 CONFIG_CMD_MII=y
+CONFIG_MII_INIT=y
 CONFIG_CMD_PING=y
 # CONFIG_CMD_SLEEP is not set
 CONFIG_OF_CONTROL=y