Revert "cmd/compile/internal/noder: limit the number of goroutine"

This reverts commit c274a7c03b.

Reason for revert: this can cause a compiler deadlock, and there's
no demonstrable benefit to making the change.

Change-Id: I42325ddea68d37db16fd0061c5baaee112b755b7
Reviewed-on: https://go-review.googlesource.com/c/go/+/308369
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>

src/cmd/compile/internal/noder/noder.go

@@ -46,8 +46,8 @@ func LoadPackage(filenames []string) {
 		noders[i] = &p
 
 		filename := filename
-		sem <- struct{}{}
 		go func() {
+			sem <- struct{}{}
 			defer func() { <-sem }()
 			defer close(p.err)
 			fbase := syntax.NewFileBase(filename)