powerpc/powernv: Implement MSI support for p5ioc2 PCIe

This implements support for MSIs on p5ioc2 PHBs. We only support
MSIs on the PCIe PHBs, not the PCI-X ones as the later hasn't been
properly verified in HW.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --cc arch/powerpc/platforms/powernv/pci-p5ioc2.c
Simple merge

diff --cc arch/powerpc/platforms/powernv/pci.c
Simple merge

diff --cc arch/powerpc/platforms/powernv/pci.h
Simple merge