powerpc/t104xrdb: Add basic ethernet support

powerpc/t104xrdb: Add basic ethernet support

This covers only non-L2 switch ethernet interfaces i.e.
RGMII and SGMII interface for both T1040RDB and T1042RDB_PI

T1040RDB is configured as serdes protocol 0x66 which can
support following interfaces
    2 RGMIIS on DTSEC4, DTSEC5
    1 SGMII on DTSEC3

T1042RDB_PI is configured as serdes protocol 0x06 which can
support following interfaces
    2 RGMIIS on DTSEC4, DTSEC5

Signed-off-by: Poonam Aggrwal <poonam.aggrwal@freescale.com>
Signed-off-by: Priyanka Jain <Priyanka.Jain@freescale.com>
[York Sun: Minor change in commit message]
Signed-off-by: York Sun <yorksun@freescale.com>