cmd/compile: un-hide closure func in init function

cmd/compile: un-hide closure func in init function

Same as CL 492135, but for init function.

Fixes #62277

Change-Id: If5ff9bc2ce2a73193b1f7ee5f7f14045d1354f56
Reviewed-on: https://go-review.googlesource.com/c/go/+/522956
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>