net: eth: altera: Change access ports to mdio for all xMII applications

Change use of Altera TSE's MDIO access from phy 0 registers to phy 1
registers. This allows support for GMII, MII, RGMII, and SGMII
designs where the external PHY is always accesible through
Altera TSE's MDIO phy 1 registers and Altera's PCS is accessible
through MDIO phy 0 registers for SGMII applications.

Signed-off-by: Vince Bridgers <vbridger@opensource.altera.com>
Tested-by: Kai Lin Ng <kailng@altera.com>
Tested-by: Dalon Westergreen <dwesterg@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>