target/loongarch: Implement xvsat

This patch includes:
- XVSAT.{B/H/W/D}[U].

Signed-off-by: Song Gao <gaosong@loongson.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230914022645.1151356-29-gaosong@loongson.cn>
4 files changed