net: sh_eth: modify the PHY_INTERFACE_MODE

The previous code had hardcoded the PHY_INTERFACE_MODE_MII of phy_connect.
So some Gigabit PHYs will not behave correctly.
The patch adds the phy_interface in sh_eth_plat_data, so we can select
the phy interface.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>