pseries/iommu: Add missing kfree

At this point, window has not been stored anywhere, so it has to be freed
before leaving the function.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@exists@
local idexpression x;
statement S,S1;
expression E;
identifier fl;
expression *ptr != NULL;
@@

x = \(kmalloc\|kzalloc\|kcalloc\)(...);
...
if (x == NULL) S
<... when != x
     when != if (...) { <+...kfree(x)...+> }
     when any
     when != true x == NULL
x->fl
...>
(
if (x == NULL) S1
|
if (...) { ... when != x
               when forall
(
 return \(0\|<+...x...+>\|ptr\);
|
* return ...;
)
}
)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Acked-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/pseries/iommu.c

@@ -939,14 +939,14 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	if (ret) {
 		dev_info(&dev->dev, "failed to map direct window for %s: %d\n",
 			 dn->full_name, ret);
-		goto out_clear_window;
+		goto out_free_window;
 	}
 
 	ret = prom_add_property(pdn, win64);
 	if (ret) {
 		dev_err(&dev->dev, "unable to add dma window property for %s: %d",
 			 pdn->full_name, ret);
-		goto out_clear_window;
+		goto out_free_window;
 	}
 
 	window->device = pdn;
@@ -958,6 +958,9 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	dma_addr = of_read_number(&create.addr_hi, 2);
 	goto out_unlock;
 
+out_free_window:
+	kfree(window);
+
 out_clear_window:
 	remove_ddw(pdn);