patman: Add an option to create patches without binary contents

Some mailing lists have size limits and when we add binary contents
to our patches it's easy to exceed the size limits.

Git supports a command line option "--no-binary" to generate patches
without any binary contents. Add an option in patman to handle this.
Note with this option patches cannot be applied properly, but they
are still useful for code review.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/patman/README b/tools/patman/README
index 02d5829..f40defb 100644
--- a/tools/patman/README
+++ b/tools/patman/README
@@ -474,6 +474,11 @@
 not later when you can't remember which patch you changed. You can always
 go back and change or remove logs from commits.
 
+7. Some mailing lists have size limits and when we add binary contents to
+our patches it's easy to exceed the size limits. Use "--no-binary" to
+generate patches without any binary contents. You are supposed to include
+a link to a git repository in your "Commit-notes", "Series-notes" or
+"Cover-letter" for maintainers to fetch the original commit.
 
 Other thoughts
 ==============