powerpc/85xx: Add basic support for P1023RDS board

The P1023RDS board is the reference board for the P1023 SoC.

Add support for booting it from NOR or NAND, with fixed 2G of DDR, PCIe,
UART, I2C, etc.

Signed-off-by: Roy Zang <tie-fei.zang@freescale.com>
Signed-off-by: Haiying Wang <Haiying.Wang@freescale.com>
Signed-off-by: Chunhe Lan <Chunhe.Lan@freescale.com>
Signed-off-by: Lei Xu <B33228@freescale.com>
Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>