target/loongarch: Allow user enable/disable LSX/LASX features

Some users may not need LSX/LASX, this patch allows the user
enable/disable LSX/LASX features.

 e.g
 '-cpu max,lsx=on,lasx=on'   (default);
 '-cpu max,lsx=on,lasx=off'  (enabled LSX);
 '-cpu max,lsx=off,lasx=on'  (enabled LASX, LSX);
 '-cpu max,lsx=off'          (disable LSX and LASX).

Signed-off-by: Song Gao <gaosong@loongson.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20231020084925.3457084-3-gaosong@loongson.cn>
2 files changed