uboot-imx

powerpc/p1010rdb: add p1010rdb-pb support with updating p1010rdb-pa

- Rename old P1010RDB board as P1010RDB-PA.
- Add support for new P1010RDB-PB board.
- Some optimization.

For more details, see board/freescale/p1010rdb/README.

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@freescale.com>
[York Sun: fix conflicts in boards.cfg]
Acked-by: York Sun <yorksun@freescale.com>