powerpc/B4860: enable PBL tool for B4860

Use a default RCW of protocol 0x2A_0x98, and a PBI configure file which
uses CPC1 as 512KB SRAM, then PBL tool can be used on B4860 to build a
pbl boot image.

Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>