[POWERPC] Create and use set_pci_dma_ops

This will allow us to build without PCI easier.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/platforms/iseries/iommu.c b/arch/powerpc/platforms/iseries/iommu.c
index d7a756d..7df2902 100644
--- a/arch/powerpc/platforms/iseries/iommu.c
+++ b/arch/powerpc/platforms/iseries/iommu.c
@@ -194,5 +194,5 @@
 	ppc_md.tce_build = tce_build_iSeries;
 	ppc_md.tce_free  = tce_free_iSeries;
 
-	pci_dma_ops = &dma_iommu_ops;
+	set_pci_dma_ops(&dma_iommu_ops);
 }