drm/ttm: Clean usage of ttm_io_prot() with TTM_PL_FLAG_CACHED

Today, most callers of ttm_io_prot() check TTM_PL_FLAG_CACHED before
calling it since on some archs it will unconditionally create non-cached
mappings.

But not all callers do which is incorrect as far as I can tell.

Instead, move that check inside ttm_io_port() itself for all archs
and make powerpc use the same implementation as ia64 and arm

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index d05437f..8fb7213 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -197,9 +197,8 @@
 						cvma.vm_page_prot);
 	} else {
 		ttm = bo->ttm;
-		if (!(bo->mem.placement & TTM_PL_FLAG_CACHED))
-			cvma.vm_page_prot = ttm_io_prot(bo->mem.placement,
-							cvma.vm_page_prot);
+		cvma.vm_page_prot = ttm_io_prot(bo->mem.placement,
+						cvma.vm_page_prot);
 
 		/* Allocate all page at once, most common usage */
 		if (ttm->bdev->driver->ttm_tt_populate(ttm)) {