These will be used to generate unique id strings for ramblocks.  The name
field is required, the device pointer is optional as most callers don't
have a device.  When there's no device or the device isn't a child of
a bus implementing BusInfo.get_dev_path, the name should be unique for
the platform.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>