crypto/x509: fix typo in comment.

Fixes #6633.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/40720046

src/pkg/crypto/x509/x509.go

@@ -1355,7 +1355,7 @@ func subjectBytes(cert *Certificate) ([]byte, error) {
 // The returned slice is the certificate in DER encoding.
 //
 // The only supported key types are RSA and ECDSA (*rsa.PublicKey or
-// *ecdsa.PublicKey for pub, *rsa.PrivateKey or *ecdsa.PublicKey for priv).
+// *ecdsa.PublicKey for pub, *rsa.PrivateKey or *ecdsa.PrivateKey for priv).
 func CreateCertificate(rand io.Reader, template, parent *Certificate, pub interface{}, priv interface{}) (cert []byte, err error) {
 	var publicKeyBytes []byte
 	var publicKeyAlgorithm pkix.AlgorithmIdentifier