libgo: correct Makefile typo in path to x/net/route package

Change-Id: Ic95831c5dfec96da8cd66db61448a163cee8d872
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/262342
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Than McIntosh <thanm@google.com>
2 files changed