PCI: vmd: Assign membar addresses from shadow registers

Certain VMD devices have registers within membar 2 which may shadow the
membar 1 and membar 2 addresses. These are intended to be used in
virtualization, where assigning a guest address wouldn't be translated
in the assignment to root port and child devices because the addresses
exist within the assignment message.

These values will only reflect the membars when enabled in the BIOS, as
determined by a register in the VMD device.

This patch declares this option as a bit in the pci id driver_data, so
that future conforming device ids can be enabled through sysfs new_id if
necessary.

Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
[lorenzo.pieralisi@arm.com: updated commit subject]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>