powerpc/64s/iommu: Don't use atomic_ function on atomic64_t type

Signed-off-by: Nicholas Piggin <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/powerpc/mm/book3s64/iommu_api.c

···
 		goto unlock_exit;
 
 	/* Are there still mappings? */
-	if (atomic_cmpxchg(&mem->mapped, 1, 0) != 1) {
+	if (atomic64_cmpxchg(&mem->mapped, 1, 0) != 1) {
 		++mem->used;
 		ret = -EBUSY;
 		goto unlock_exit;