cmd/compile: add missing copyright notice

Also, simplify one expression (missed comment on previous review).

Change-Id: Ic2d212442c2738e03c733336bb990e28c8912ca4
Reviewed-on: https://go-review.googlesource.com/c/go/+/379254
Trust: Dan Scales <[email protected]>
Run-TryBot: Dan Scales <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>

Author: danscales

src/cmd/compile/internal/types/structuraltype.go

@@ -1,3 +1,7 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 package types
 
 // Implementation of structural type computation for types.
@@ -107,7 +111,7 @@ func specificTypes(t *Type) (list []term, inf bool) {
 		default:
 			// m.Type is a single non-interface type, so r2 is just a
 			// one-element list, inf2 is false.
-			r2 = []term{term{false, m.Type}}
+			r2 = []term{{false, m.Type}}
 		}
 
 		if inf2 {