cmd/internal/obj/loong64: add {V,XV}SEQI, {V,XV}.{AND,OR,XOR,NOR} instructions support

cmd/internal/obj/loong64: add {V,XV}SEQI, {V,XV}.{AND,OR,XOR,NOR} instructions support

Go asm syntax:
         VSEQB  $1, V2, V3
        XVSEQB  $2, X2, X3
         V{AND,OR,XOR,NOR}B  $1, V2, V3
        XV{AND,OR,XOR,NOR}B  $1, V2, V3
         V{AND,OR,XOR,NOR,ANDN,ORN}V V1, V2, V3
        XV{AND,OR,XOR,NOR,ANDN,ORN}V V1, V2, V3

Equivalent platform assembler syntax:
         vseqi.b v3, v2, $1
        xvseqi.b x3, x2 ,$2
         v{and,or,xor,nor}.b  v3, v2, $1
        xv{and,or,xor,nor}.b  x3, x2, $1
         v{and,or,xor,nor,andn,orn}v v3, v2, v1
        xv{and,or,xor,nor,andn,orn}v x3, x2, x1

Change-Id: I56ae0db72c7f473755cbdc7f7171c1058a9def97
Reviewed-on: https://go-review.googlesource.com/c/go/+/635515
Reviewed-by: Meidan Li <limeidan@loongson.cn>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: David Chase <drchase@google.com>