moveconfig: Use an encoding with open()

Fix pylint warnings about needing an explicit character encoding.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/moveconfig.py b/tools/moveconfig.py
index d46433c..9b71659 100755
--- a/tools/moveconfig.py
+++ b/tools/moveconfig.py
@@ -1457,12 +1457,14 @@
 
     # Write out the updated information
     if do_update:
-        with open(os.path.join(path, 'scripts', 'conf_nospl'), 'w') as out:
+        with open(os.path.join(path, 'scripts', 'conf_nospl'), 'w',
+                  encoding='utf-8') as out:
             print('# These options should not be enabled in SPL builds\n',
                   file=out)
             for item in sorted(spl_not_found):
                 print(item, file=out)
-        with open(os.path.join(path, 'scripts', 'conf_noproper'), 'w') as out:
+        with open(os.path.join(path, 'scripts', 'conf_noproper'), 'w',
+                  encoding='utf-8') as out:
             print('# These options should not be enabled in Proper builds\n',
                   file=out)
             for item in sorted(proper_not_found):