vfio/spapr_tce: Check kzalloc() return when preregistering memory

This adds missing checking for kzalloc() return value.

Fixes: 4b6fad7097f8 ("powerpc/mm/iommu, vfio/spapr: Put pages on VFIO container shutdown")
Signed-off-by: Alexey Kardashevskiy <[e-mail]>
Reviewed-by: David Gibson <[e-mail]>
Signed-off-by: Alex Williamson <[e-mail]>

drivers/vfio/vfio_iommu_spapr_tce.c

···
 		return ret;
 
 	tcemem = kzalloc(sizeof(*tcemem), GFP_KERNEL);
+	if (!tcemem) {
+		mm_iommu_put(container->mm, mem);
+		return -ENOMEM;
+	}
+
 	tcemem->mem = mem;
 	list_add(&tcemem->next, &container->prereg_list);