kvm/iommu: fix compile warning

This fixes a compile warning about a variable thats maybe used
uninitialized in the function.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
index d0bebaa..e9693a2 100644
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -71,7 +71,7 @@
 
 static int kvm_iommu_map_memslots(struct kvm *kvm)
 {
-	int i, r;
+	int i, r = 0;
 
 	down_read(&kvm->slots_lock);
 	for (i = 0; i < kvm->nmemslots; i++) {