fix patman --limit-cc option

patman's --limit-cc option parses its argument to an integer and uses
that to trim the list of CC recipients to a particular maximum. but that
only works if the cc variable is a list, which it is not.

Signed-off-by: Bernhard Kirchen <bernhard.kirchen@mbconnectline.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

tools/patman/series.py

@@ -271,7 +271,7 @@ class Series(dict):
                 cc += get_maintainer.GetMaintainer(dir_list, commit.patch)
             for x in set(cc) & set(settings.bounces):
                 print(col.Color(col.YELLOW, 'Skipping "%s"' % x))
-            cc = set(cc) - set(settings.bounces)
+            cc = list(set(cc) - set(settings.bounces))
             if limit is not None:
                 cc = cc[:limit]
             all_ccs += cc