dontdiff: add generated

We move more and more stuff to include/generated - so lets ignore the
content for users of plain diff.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>

Documentation/dontdiff

@@ -103,6 +103,7 @@ gconf
 gen-devlist
 gen_crc32table
 gen_init_cpio
+generated
 genheaders
 genksyms
 *_gray256.c