powerpc/pseries/iommu: Use correct return type in dupe_ddw_if_already_created

Otherwise we get silent truncations.

Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Milton Miller <miltonm@bga.com>
Cc: linuxppc-dev@ozlabs.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/pseries/iommu.c

@@ -693,7 +693,7 @@ static void remove_ddw(struct device_node *np)
 }
 
 
-static int dupe_ddw_if_already_created(struct pci_dev *dev, struct device_node *pdn)
+static u64 dupe_ddw_if_already_created(struct pci_dev *dev, struct device_node *pdn)
 {
 	struct device_node *dn;
 	struct pci_dn *pcidn;