[POWERPC] 85xx: Add initial MPC8544 DS platform files.

This patch provides the basic MPC8544 DS platform code and config.
Follow-up patches will add peripherals such as PCI and SATA.

Signed-off-by: Xianghua Xiao <x.xiao@freescale.com>
Signed-off-by: Roy Zang <tie-fei.zang@freescale.com>
Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: Jon Loeliger <jdl@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>