powerpc/85xx: Add PBL boot from SPI flash support on P4080DS

PBL(pre-boot loader): SPI flash used as RCW(Reset Configuration Word) and
PBI(pre-boot initialization) source, CPC(CoreNet Platform Cache) used as
1M SRAM where PBL will copy whole U-BOOT image to, U-boot can boot from
CPC after PBL completes RCW and PBI phases.

Signed-off-by: Chunhe Lan <b25806@freescale.com>
Signed-off-by: Mingkai Hu <Mingkai.hu@freescale.com>
Signed-off-by: Shaohui Xie <b21989@freescale.com>
Signed-off-by: Roy Zang <tie-fei.zang@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>