gianfar: remove gianfar_mii.c

commit 1577ecef
Author: Andy Fleming <afleming@freescale.com>
Date:   Wed Feb 4 16:42:12 2009 -0800

    netdev: Merge UCC and gianfar MDIO bus drivers

left out the deletion of gianfar_mii.c.

Signed-off-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>