drm/ast: switch to using CACHED by default for sysram

This fixes problems on ppc64 platforms, where we could end up using
a WC mapping for migrating BOs with memcpy, when really we want to
use cached memory.

Tested-by: Ben Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/ast/ast_ttm.c

@@ -300,9 +300,9 @@ void ast_ttm_placement(struct ast_bo *bo, int domain)
 	if (domain & TTM_PL_FLAG_VRAM)
 		bo->placements[c++].flags = TTM_PL_FLAG_WC | TTM_PL_FLAG_UNCACHED | TTM_PL_FLAG_VRAM;
 	if (domain & TTM_PL_FLAG_SYSTEM)
-		bo->placements[c++].flags = TTM_PL_MASK_CACHING | TTM_PL_FLAG_SYSTEM;
+		bo->placements[c++].flags = TTM_PL_FLAG_CACHED | TTM_PL_FLAG_SYSTEM;
 	if (!c)
-		bo->placements[c++].flags = TTM_PL_MASK_CACHING | TTM_PL_FLAG_SYSTEM;
+		bo->placements[c++].flags = TTM_PL_FLAG_CACHED | TTM_PL_FLAG_SYSTEM;
 	bo->placement.num_placement = c;
 	bo->placement.num_busy_placement = c;
 	for (i = 0; i < c; ++i) {