sparc64: Propagate PCI device archdata into OF device tree for EBUS.

In order to convert EBUS drivers doing DMA into pure OF drivers,
we need the of_device->dev.archdata setup properly.

EBUS instances that can provide DMA for device nodes sit on PCI,
so detect and propagate the information there.

Signed-off-by: David S. Miller <davem@davemloft.net>