cmd/compile: do not push functions literal node to Func.Dcl

They are skipped while processing Func.Dcl anyway.

This CL does not pass toolstash-check, because it reduces the length
of Func.Dcl length, while that length is used to generate autotmp
variables name.

Change-Id: I408183e62ce6c34e5f04c89814ebb9570957e37b
Reviewed-on: https://go-review.googlesource.com/c/go/+/252418


Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>