powerpc/85xx: fix null pointer dereference when init the SGMII TBI PHY

powerpc/85xx: fix null pointer dereference when init the SGMII TBI PHY

Function dtsec_configure_serdes() needs to know where the TBI PHY registers
are in order to configure SGMII for proper SerDes operation.

During SGMII initialzation, fm_eth_init_mac() passing NULL for 'phyregs'
when it called init_dtsec(), because it was believed that phyregs was not
used.  In fact, it is used by dtsec_configure_serdes() to configure the TBI
PHY registers.

We also need to define the PHY registers in struct fm_mdio.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>