tcg/loongarch64: Lower vector shift integer ops

Lower the following ops:

- shli_vec
- shrv_vec
- sarv_vec

Signed-off-by: Jiajie Chen <c@jia.je>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230908022302.180442-14-c@jia.je>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>