go/types: fix type in Interface.Complete method

This doesn't appear to have caused problems (because we don't depend
on the sort order, it seems) but it's clearly incorrect.

Change-Id: Ib6eb0128a3c17997c7907a618f9ce102b32aaa98
Reviewed-on: https://go-review.googlesource.com/79497Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/go/types/type.go

@@ -262,7 +262,7 @@ func NewInterface(methods []*Func, embeddeds []*Named) *Interface {
 	}
 	sort.Sort(byUniqueMethodName(methods))
 
-	if embeddeds == nil {
+	if embeddeds != nil {
 		sort.Sort(byUniqueTypeName(embeddeds))
 	}