powerpc/b4860qds: Slave module for boot from SRIO and PCIE

When a b4860qds board boots from SRIO or PCIE, it needs to finish these
processes:
	1. Set all the cores in holdoff status.
	2. Set the boot location to one PCIE or SRIO interface by RCW.
	3. Set a specific TLB entry for the boot process.
	4. Set a LAW entry with the TargetID of one PCIE or SRIO for the boot.
	5. Set a specific TLB entry in order to fetch ucode and ENV from
	   master.
	6. Set a LAW entry with the TargetID one of the PCIE ports for
	   ucode and ENV.
	7. Slave's u-boot image should be generated specifically by
	   make xxxx_SRIO_PCIE_BOOT_config.
	   This will set SYS_TEXT_BASE=0xFFF80000 and other configurations.

For more information about the feature of Boot from SRIO/PCIE, please
refer to the document doc/README.srio-pcie-boot-corenet.

Signed-off-by: Liu Gang <Gang.Liu@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>