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

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201111110723.3148665-3-npiggin@gmail.com

arch/powerpc/mm/book3s64/iommu_api.c

@@ -263,7 +263,7 @@ long mm_iommu_put(struct mm_struct *mm, struct mm_iommu_table_group_mem_t *mem)
 		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;