powerpc/iommu: Put IOMMU group explicitly

So far an iommu_table lifetime was the same as PE. Dynamic DMA windows
will change this and iommu_free_table() will not always require
the group to be released.

This moves iommu_group_put() out of iommu_free_table().

This adds a iommu_pseries_free_table() helper which does
iommu_group_put() and iommu_free_table(). Later it will be
changed to receive a table_group and we will have to change less
lines then.

This should cause no behavioural change.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/iommu.c

@@ -726,13 +726,6 @@ void iommu_free_table(struct iommu_table *tbl, const char *node_name)
 	if (tbl->it_offset == 0)
 		clear_bit(0, tbl->it_map);
 
-#ifdef CONFIG_IOMMU_API
-	if (tbl->it_group) {
-		iommu_group_put(tbl->it_group);
-		BUG_ON(tbl->it_group);
-	}
-#endif
-
 	/* verify that table contains no entries */
 	if (!bitmap_empty(tbl->it_map, tbl->it_size))
 		pr_warn("%s: Unexpected TCEs for %s\n", __func__, node_name);