patman: Handle invalid characters in patch files

In some cases latin1 encoding may be used in source files. If
'high-ascii' are used, patman may report an error:

   UnicodeDecodeError: 'utf-8' codec can't decode byte 0xf3 in
      position 1051: invalid continuation byte

Fix this by replacing these characters. This may cause the patch to fail
to apply, but at least it can be checked.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/patman/patchstream.py

@@ -831,7 +831,7 @@ def fix_patch(backup_dir, fname, series, cmt, keep_change_id=False,
     fname = os.path.join(cwd or '', fname)
     handle, tmpname = tempfile.mkstemp()
     outfd = os.fdopen(handle, 'w', encoding='utf-8')
-    infd = open(fname, 'r', encoding='utf-8')
+    infd = open(fname, 'r', encoding='utf-8', errors='replace')
     pst = PatchStream(series, keep_change_id=keep_change_id,
                       insert_base_commit=insert_base_commit)
     pst.commit = cmt