Some files were missing from the libgo copy of internal/cpu, because they
used to only declare CacheLinePadSize which libgo gets from goarch.sh.
Now they also declare doinit, so copy them over. Adjust cpu_other.go.
Fix the amd64p32 build by adding a build constraint to cpu_no_name.go.
Fixes PR go/98493
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/281472
a9f76d03bb