ppc/P1_P2_RDB: On-chip BootROM support

On Chip BootROM support for P1 and P2 series RDB platforms.

This patch is derived from latest On Chip BootROM support on MPC8536DS

Signed-off-by: Dipen Dudhat <dipen.dudhat@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>