net: davinci_emac: cleanup unused mdio emac code

This patch removes code that has been rendered useless by the previous patches
in this series.

Signed-off-by: Cyril Chemparathy <cyril@ti.com>
Acked-by: David S. Miller <davem@davemloft.net>
Tested-by: Michael Williamson <michael.williamson@criticallink.com>
Tested-by: Caglar Akyuz <caglarakyuz@gmail.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>