Update rules for contributing external code

We can merge the spatch and reformatting steps into one commit.  Those
steps (and their fixups) are just part of an "automated conversion" commit.

Signed-off-by: Barret Rhoden <brho@cs.berkeley.edu>

Documentation/Contributing.md

diff --git a/Documentation/Contributing.md b/Documentation/Contributing.md
index 84ba6cc..d31b86d 100644
--- a/Documentation/Contributing.md
+++ b/Documentation/Contributing.md
@@ -121,10 +121,10 @@
 must say where you got the code from, such as a URL, project name and version,
 etc.  Do not add the .c files to Kbuild yet.  Otherwise, you'll break the build.
 
-+ Run spatch, if applicable, in a single commit.
-
-+ Run clang-format, if applicable, in a single commit.  It's much easier to
-diagnose problems if spatch and reformatting was done before any other changes.
++ Run spatch and clang-format, if applicable, in a single commit.  It's much
+easier to diagnose problems if spatch and reformatting was done before any
+other changes.  Sometimes these tools fail.  Just fix up any mistakes in this
+commit.
 
 + Add your own changes, such that it compiles.  This is the point where you add
 the .c files to Kbuild so that we actually build the files.