Add info about whitespace to SubmitChecklist

Signed-off-by: NRoland Dreier <rolandd@cisco.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Documentation/SubmitChecklist

@@ -80,3 +80,7 @@ kernel patches.
 23: Tested after it has been merged into the -mm patchset to make sure
     that it still works with all of the other queued patches and various
     changes in the VM, VFS, and other subsystems.
+
+24: Avoid whitespace damage such as indenting with spaces or whitespace
+    at the end of lines.  You can test this by feeding the patch to
+    "git apply --check --whitespace=error-all"