powerpc/85xx: add P1020MBG-PC platform support

powerpc/85xx: add P1020MBG-PC platform support

The p1020mbg-pc has the similar feature as the p1020rdb.
Therefore, p1020mbg-pc use the same platform file as the p1/p2 rdb board.
Overview of P1020MBG-PC platform:
        - DDR3 2GB
        - NOR flash 64MB
        - I2C EEPROM 256Kb
        - eTSEC1 (RGMII PHY) connected to VSC7385 L2 switch
        - eTSEC2 (SGMII PHY)
        - eTSEC3 (RGMII PHY)
        - SDHC
        - 2 USB ports
        - 4 TDM ports
        - PCIe (Lane1 to dual SATA controller)

Signed-off-by: Jerry Huang <Chang-Ming.Huang@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>