powerpc/powernv: Pick M64 PEs based on BARs

powerpc/powernv: Pick M64 PEs based on BARs

On PHB3, PE might be reserved in advance to reflect the M64 segments
consumed by the PE according to M64 BARs (exclude VF BARs) of the PCI
devices included in the PE. The PE is picked based on M64 BARs instead
of the bridge's M64 windows, which might include VF BARs. Otherwise,
wrong PE could be picked.

The patch calculates the used M64 segments and PE numbers according to
the M64 BARs, excluding VF BARs, of PCI devices in one particular PE,
instead of the bridge's M64 windows. Then the right PE number is picked.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>