powerpc/cell: move dma direct window setup out of dma_configure

Configure the dma settings at device setup time, and stop playing games
with get_pci_dma_ops.  This prepares for using the common dma_configure
code later on.

Includes fixes from Michael Ellerman.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>