drm/ttm: optimize bo_kmap_type values

A micro-optimization on the function ttm_kmap_obj_virtual().

By defining the values of enum ttm_bo_kmap_obj::bo_kmap_type to have a
bit indicating iomem, size of the function ttm_kmap_obj_virtual() will be
reduced by 16 bytes on x86_64 (gcc 4.1.2).

ttm_kmap_obj_virtual() may be heavily used, when buffer objects are
accessed via wrappers, that work for both kinds of memory addresses:
iomem cookies and kernel virtual.
Signed-off-by: NPekka Paalanen <pq@iki.fi>
Signed-off-by: NDave Airlie <airlied@redhat.com>

include/drm/ttm/ttm_bo_api.h

@@ -245,14 +245,15 @@ struct ttm_buffer_object {
  * premapped region.
  */
 
+#define TTM_BO_MAP_IOMEM_MASK 0x80
 struct ttm_bo_kmap_obj {
 	void *virtual;
 	struct page *page;
 	enum {
-		ttm_bo_map_iomap,
-		ttm_bo_map_vmap,
-		ttm_bo_map_kmap,
-		ttm_bo_map_premapped,
+		ttm_bo_map_iomap        = 1 | TTM_BO_MAP_IOMEM_MASK,
+		ttm_bo_map_vmap         = 2,
+		ttm_bo_map_kmap         = 3,
+		ttm_bo_map_premapped    = 4 | TTM_BO_MAP_IOMEM_MASK,
 	} bo_kmap_type;
 };
 
@@ -522,8 +523,7 @@ extern int ttm_bo_evict_mm(struct ttm_bo_device *bdev, unsigned mem_type);
 static inline void *ttm_kmap_obj_virtual(struct ttm_bo_kmap_obj *map,
 					 bool *is_iomem)
 {
-	*is_iomem = (map->bo_kmap_type == ttm_bo_map_iomap ||
-		     map->bo_kmap_type == ttm_bo_map_premapped);
+	*is_iomem = !!(map->bo_kmap_type & TTM_BO_MAP_IOMEM_MASK);
 	return map->virtual;
 }