cmd/compile: remove two out-of-phase calls to walk

All calls to walkstmt/walkexpr/etc should be rooted from funccompile,
whereas transformclosure and fninit are called by main.

Passes toolstash-check.

Change-Id: Ic880e2d2d83af09618ce4daa8e7716f6b389e53e
Reviewed-on: https://go-review.googlesource.com/99418
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

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

@@ -417,7 +417,6 @@ func transformclosure(xfunc *Node) {
 
 		if len(body) > 0 {
 			typecheckslice(body, Etop)
-			walkstmtlist(body)
 			xfunc.Func.Enter.Set(body)
 			xfunc.Func.SetNeedctxt(true)
 		}

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

@@ -182,7 +182,6 @@ func fninit(n []*Node) {
 		loop.Ninit.Set1(zero)
 
 		loop = typecheck(loop, Etop)
-		loop = walkstmt(loop)
 		r = append(r, loop)
 	}