Remove duplicated code in SBC8548 board and utilize the common
fsl_pcie_init_board().  We also now dynamically setup the LAWs for PCI
controllers based on which PCIe controllers are enabled.
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>
Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>