target/loongarch: Implement vfrstp

This patch includes:
- VFRSTP[I].{B/H}.

Acked-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Song Gao <gaosong@loongson.cn>
Message-Id: <20230504122810.4094787-33-gaosong@loongson.cn>
5 files changed