cmd/internal/obj/loong64: add support for instructions ANDN and ORN

cmd/internal/obj/loong64: add support for instructions ANDN and ORN

Go asm syntax:
	ANDN/ORN	RK, RJ, RD
    or  ANDN/ORN	RK, RD

Equivalent platform assembler syntax:
	andn/orn	rd, rj, rk
    or  andn/orn	rd, rd, rk

Ref: https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html

Change-Id: I6d240ecae8f9443811ca450aed3574f13f0f4a81
Reviewed-on: https://go-review.googlesource.com/c/go/+/610475
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Commit-Queue: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: abner chenc <chenguoqi@loongson.cn>