patman: Continue on if warnings are found outside a commit

While we cannot know which commit the warning relates to, this should not
be fatal. Print the warning and carry on.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/patman/patchstream.py b/tools/patman/patchstream.py
index cdcd50a..a44cd86 100644
--- a/tools/patman/patchstream.py
+++ b/tools/patman/patchstream.py
@@ -133,8 +133,8 @@
             ValueError: Warning is generated with no commit associated
         """
         if not self.commit:
-            raise ValueError('Warning outside commit: %s' % warn)
-        if warn not in self.commit.warn:
+            print('Warning outside commit: %s' % warn)
+        elif warn not in self.commit.warn:
             self.commit.warn.append(warn)
 
     def _add_to_series(self, line, name, value):