dontdiff: ignore timeconst.h

Ignore the autobuilt kernel/timeconst.h when
using diff on an built kernel tree.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/Documentation/dontdiff b/Documentation/dontdiff
index feae216..881e6dd 100644
--- a/Documentation/dontdiff
+++ b/Documentation/dontdiff
@@ -172,6 +172,7 @@
 split-include
 tags
 tftpboot.img
+timeconst.h
 times.h*
 tkparse
 trix_boot.h