cmd/compile/internal: add register info for loong64 regABI

cmd/compile/internal: add register info for loong64 regABI

Update #40724

Co-authored-by: Xiaolin Zhao <zhaoxiaolin@loongson.cn>
Change-Id: Ifd7d94147b01e4fc83978b53dca2bcc0ad1ac4e3
Reviewed-on: https://go-review.googlesource.com/c/go/+/521779
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: David Chase <drchase@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Meidan Li <limeidan@loongson.cn>