target/loongarch: Implement xvsrlr xvsrar

This patch includes:
- XVSRLR[I].{B/H/W/D};
- XVSRAR[I].{B/H/W/D}.

Signed-off-by: Song Gao <gaosong@loongson.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230914022645.1151356-38-gaosong@loongson.cn>