powerpc/fsl_pci: simplify fsl_pci_dma_set_mask

swiotlb will only bounce buffer when the effective dma address for the
device is smaller than the actual DMA range.  Instead of flipping between
the swiotlb and nommu ops for FSL SOCs that have the second outbound
window just don't set the bus dma_mask in this case.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NScott Wood <oss@buserror.net>

arch/powerpc/sysdev/fsl_pci.c

@@ -135,7 +135,7 @@ static int fsl_pci_dma_set_mask(struct device *dev, u64 dma_mask)
 	 * mapping that allows addressing any RAM address from across PCI.
 	 */
 	if (dev_is_pci(dev) && dma_mask >= pci64_dma_offset * 2 - 1) {
-		set_dma_ops(dev, &dma_nommu_ops);
+		dev->bus_dma_mask = 0;
 		set_dma_offset(dev, pci64_dma_offset);
 	}
 
@@ -395,10 +395,6 @@ static void setup_pci_atmu(struct pci_controller *hose)
 				out_be32(&pci->piw[win_idx].piwar,  piwar);
 			}
 
-			/*
-			 * install our own dma_set_mask handler to fixup dma_ops
-			 * and dma_offset
-			 */
 			ppc_md.dma_set_mask = fsl_pci_dma_set_mask;
 
 			pr_info("%pOF: Setup 64-bit PCI DMA window\n", hose->dn);