runtime: add regABI support in memclr and memmove functions on loong64

runtime: add regABI support in memclr and memmove functions on loong64

Update #40724

Co-authored-by: Xiaolin Zhao <zhaoxiaolin@loongson.cn>
Change-Id: I55c78bab5c697ea6c30f9d81f5f8fb75abb3987c
Reviewed-on: https://go-review.googlesource.com/c/go/+/521786
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Meidan Li <limeidan@loongson.cn>
Run-TryBot: David Chase <drchase@google.com>
Auto-Submit: David Chase <drchase@google.com>
Reviewed-by: David Chase <drchase@google.com>