x/crypto/ssh: run go fmt

Change-Id: Ibb071aa550ca7392543c2d1eba8f8a69ba1d86fa
Reviewed-on: https://go-review.googlesource.com/17270
Reviewed-by: Dave Cheney <dave@cheney.net>

ssh/kex.go

@@ -8,8 +8,8 @@ import (
 	"crypto"
 	"crypto/ecdsa"
 	"crypto/elliptic"
-	"crypto/subtle"
 	"crypto/rand"
+	"crypto/subtle"
 	"errors"
 	"io"
 	"math/big"