Implement pcibios_iov_resource_alignment() on powernv platform.

On PowerNV platform, there are 3 cases for the IOV BAR:
1. initial state, the IOV BAR size is multiple times of VF BAR size
2. after expanded, the IOV BAR size is expanded to meet the M64 segment size
3. sizing stage, the IOV BAR is truncated to 0

pnv_pci_iov_resource_alignment() handle these three cases respectively.

[bhelgaas: adjust to drop "align" parameter, return pci_iov_resource_size()
if no ppc_md machdep_call version]
Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>