MIPS: PCI: Multi-node PCI support for Netlogic XLP

On a multi-chip XLP board, each node can have 4 PCIe links. Update
XLP PCI code to initialize PCIe on all the nodes.

Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Patchwork: http://patchwork.linux-mips.org/patch/4803/


Signed-off-by: John Crispin <blogic@openwrt.org>