cmd/internal/obj/loong64: add support for {V,XV}SET{EQ,NE}Z.V series instructions

cmd/internal/obj/loong64: add support for {V,XV}SET{EQ,NE}Z.V series instructions

Change-Id: If3794dfde3ff461662c8a493ff51d0c779e81bca
Reviewed-on: https://go-review.googlesource.com/c/go/+/664795
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>