powerpc/pseries/iommu: Add of_node_put() before break

Fix following coccicheck warning:

./arch/powerpc/platforms/pseries/iommu.c:924:1-28: WARNING: Function
for_each_node_with_property should have of_node_put() before break

Early exits from for_each_node_with_property should decrement the
node reference counter.
Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Reviewed-by: Leonardo Bras <leobras.c@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211014075624.16344-1-wanjiabing@vivo.com

arch/powerpc/platforms/pseries/iommu.c

@@ -929,8 +929,10 @@ static void find_existing_ddw_windows_named(const char *name)
 		}
 
 		window = ddw_list_new_entry(pdn, dma64);
-		if (!window)
+		if (!window) {
+			of_node_put(pdn);
 			break;
+		}
 
 		spin_lock(&dma_win_list_lock);
 		list_add(&window->list, &dma_win_list);