cmd/compile: consistenly use CTxxx for works relate to Ctype

Passes toolstash-check

Change-Id: Iaeaf2575b9f492e45619007438c0138f9d22006c
Reviewed-on: https://go-review.googlesource.com/c/go/+/200959
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/gc/const.go

@@ -552,7 +552,7 @@ func tostr(v Val) Val {
 
 func consttype(n *Node) Ctype {
 	if n == nil || n.Op != OLITERAL {
-		return 0
+		return CTxxx
 	}
 	return n.Val().Ctype()
 }

src/cmd/compile/internal/gc/order.go

@@ -202,7 +202,7 @@ func isaddrokay(n *Node) bool {
 // The result of addrTemp MUST be assigned back to n, e.g.
 // 	n.Left = o.addrTemp(n.Left)
 func (o *Order) addrTemp(n *Node) *Node {
-	if consttype(n) > 0 {
+	if consttype(n) != CTxxx {
 		// TODO: expand this to all static composite literal nodes?
 		n = defaultlit(n, nil)
 		dowidth(n.Type)