powerpc/iommu: Add it_page_shift field to determine iommu page size

This patch adds a it_page_shift field to struct iommu_table and
initiliases it to 4K for all platforms.

Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/vio.c

@@ -1177,9 +1177,10 @@ static struct iommu_table *vio_build_iommu_table(struct vio_dev *dev)
 			    &tbl->it_index, &offset, &size);
 
 	/* TCE table size - measured in tce entries */
-	tbl->it_size = size >> IOMMU_PAGE_SHIFT_4K;
+	tbl->it_page_shift = IOMMU_PAGE_SHIFT_4K;
+	tbl->it_size = size >> tbl->it_page_shift;
 	/* offset for VIO should always be 0 */
-	tbl->it_offset = offset >> IOMMU_PAGE_SHIFT_4K;
+	tbl->it_offset = offset >> tbl->it_page_shift;
 	tbl->it_busno = 0;
 	tbl->it_type = TCE_VB;
 	tbl->it_blocksize = 16;