[dev.link] cmd/link: convert Peinit to use the loader
[dev.link] cmd/link: convert Peinit to use the loader

There is one use of sym.Symbol in Peinit, which is called from
linksetup, which is before loadlibfull. Convert this one.

Change-Id: Iedb8b0e0c5c292bccf5c9bd5d092ee434a4ebdbd
Reviewed-on: https://go-review.googlesource.com/c/go/+/221177
Run-TryBot: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Jeremy Faller <b3f594e10a9edcf5413cf1190121d45078c62290@golang.org>

nawawi/go,CAFxX/go,golang/go,nawawi/go,nawawi/go,akutz/go,akutz/go,CAFxX/go,akutz/go,CAFxX/go,akutz/go,cloudflare/go,golang/go,cloudflare/go,golang/go,akutz/go,cloudflare/go,nawawi/go,golang/go,CAFxX/go,cloudflare/go,cloudflare/go,cloudflare/go,golang/go,CAFxX/go,nawawi/go,cloudflare/go,golang/go,CAFxX/go,golang/go,CAFxX/go,nawawi/go,akutz/go,nawawi/go,golang/go,nawawi/go,akutz/go,CAFxX/go,cloudflare/go,akutz/go