cmd/compile: remove unused code in walk.Walk
no errors'll be added during ir.DumpList, no need to be check again
Change-Id: I85ae2edd4377851277e9bb2a8baa28825ac3fd90
GitHub-Last-Rev:
b35ca85e57d81002adad4b1ffc9506f359201b71
GitHub-Pull-Request: golang/go#64955
Reviewed-on: https://go-review.googlesource.com/c/go/+/553895
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>