powerpc/85xx: Rework MPC8544DS pci_init_board to use common FSL PCIe code

Remove duplicated code in MPC8544DS board and utilize the common
fsl_pcie_init_ctrl().  We also now dynamically setup the LAWs for PCI
controllers based on which PCIe controllers are enabled.

We don't use the full fsl_pcie_init_ctrl() since we have to handle PCIE3
specially to setup the additional memory map region and we utilize a
single LAW to cover the controller.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>