cmd/link: optimize PPC64 inline plt sequences if local
cmd/link: optimize PPC64 inline plt sequences if local

Indirect branches are much more expensive than direct. If the call is
known to be local, we can replace most of the operations with a nop,
and call directly.

Updates #53345

Change-Id: Icfff9ec1f6c7f8e4181f0f28976033308d2f53eb
Reviewed-on: https://go-review.googlesource.com/c/go/+/412715
Reviewed-by: Cherry Mui <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
Run-TryBot: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@google.com>
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go