translate the "timestamping.rst" into Simplified Chinese.
Update the translation through commit d5c17e3654
("docs: networking: timestamping: improve stacked PHC sentence")
Signed-off-by: Wang Yaxin <wang.yaxin@zte.com.cn>
Signed-off-by: Sun yuxi <sun.yuxi@zte.com.cn>
Reviewed-by: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: Alex Shi <alexs@kernel.org>
