crypto/md5: make receiver name consistent

Fixes go lint warning.

Change-Id: I2d73208c6841f35d7a21a1fb4cfafbbd4250228f
Reviewed-on: https://go-review.googlesource.com/108659Reviewed-by: Iskander Sharipov <iskander.sharipov@intel.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/crypto/md5/md5.go

@@ -160,10 +160,10 @@ func (d *digest) Write(p []byte) (nn int, err error) {
 	return
 }
 
-func (d0 *digest) Sum(in []byte) []byte {
-	// Make a copy of d0 so that caller can keep writing and summing.
-	d := *d0
-	hash := d.checkSum()
+func (d *digest) Sum(in []byte) []byte {
+	// Make a copy of d so that caller can keep writing and summing.
+	d0 := *d
+	hash := d0.checkSum()
 	return append(in, hash[:]...)
 }