drm/ttm:fix wrong decoding of bo_count

we observe abnormal number from:
/sys/devices/virtual/drm/amdttm/buffer_objects/bo_count

bo_count is atomic_inc which is "int" type,
shouldn't explicitly turn it to unsigned long.
Signed-off-by: Monk Liu <monk.liu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/ttm/ttm_bo.c

@@ -109,8 +109,8 @@ static ssize_t ttm_bo_global_show(struct kobject *kobj,
 	struct ttm_bo_global *glob =
 		container_of(kobj, struct ttm_bo_global, kobj);
 
-	return snprintf(buffer, PAGE_SIZE, "%lu\n",
-			(unsigned long) atomic_read(&glob->bo_count));
+	return snprintf(buffer, PAGE_SIZE, "%d\n",
+				atomic_read(&glob->bo_count));
 }
 
 static struct attribute *ttm_bo_global_attrs[] = {