docs/zh_CN: update Li Yang's email address

Change leoli@freescale.com and leo@zh-kernel.org to active address:
leoyang.li@nxp.com

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Weiwei Jia <harryxiyou@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>