crypto: add codereview.cfg

See golang.org/cl/4131 for context.

Change-Id: I050ffde0bec2c2fd639e028e1abb22a720e1b2eb
Reviewed-on: https://go-review.googlesource.com/7761
Reviewed-by: David Crawshaw <crawshaw@golang.org>

codereview.cfg

@@ -0,0 +1 @@
+issuerepo: golang/go