patman: fix coverletter cc list with nulls

fixes: 8ab452d587

When compiling list of cover letter cc addresses, using null as a
separater, then encoding to utf-8 results in lots of "\x00" as
separators. patman then doesnt understand that when it comes to
repoting the list to send-email.

Fix this by not encoding to utf-8, as done for the other patch files.

Signed-off-by: Robert Beckett <bob.beckett@collabora.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

tools/patman/series.py

@@ -251,7 +251,7 @@ class Series(dict):
             cover_cc = [tools.FromUnicode(m) for m in cover_cc]
             cc_list = '\0'.join([tools.ToUnicode(x)
                                  for x in sorted(set(cover_cc + all_ccs))])
-            print(cover_fname, cc_list.encode('utf-8'), file=fd)
+            print(cover_fname, cc_list, file=fd)
 
         fd.close()
         return fname