vfio/spapr: Fix missing mutex unlock when creating a window

Commit d9c72894 ("vfio/spapr: Postpone default window creation")
added an additional exit to the VFIO_IOMMU_SPAPR_TCE_CREATE case and
made it possible to return from tce_iommu_ioctl() without unlocking
container->lock; this fixes the issue.

Fixes: d9c72894 ("vfio/spapr: Postpone default window creation")
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/vfio_iommu_spapr_tce.c

@@ -1123,10 +1123,9 @@ static long tce_iommu_ioctl(void *iommu_data,
 		mutex_lock(&container->lock);
 
 		ret = tce_iommu_create_default_window(container);
-		if (ret)
-			return ret;
-
-		ret = tce_iommu_create_window(container, create.page_shift,
+		if (!ret)
+			ret = tce_iommu_create_window(container,
+					create.page_shift,
 					create.window_size, create.levels,
 					&create.start_addr);