Convert CONFIG_MII_INIT to Kconfig

This converts the following to Kconfig:
   CONFIG_MII_INIT

Signed-off-by: Tom Rini <trini@konsulko.com>

cmd/Kconfig

@@ -1658,6 +1658,10 @@ config CMD_MII
 	  to management parameters and services.
 	  The interface is referred to as the MII management interface.
 
+config MII_INIT
+	bool "Call mii_init() in the mii command"
+	depends on CMD_MII && (MPC8XX_FEC || FSLDMAFE || MCFFEC)
+
 config CMD_MDIO
 	bool "mdio"
 	depends on PHYLIB