doc/zh_CN: adjust table markup in mips/ingenic-tcu.rst

Commit 419b1d4e ("doc/zh_CN: add mips ingenic-tcu.rst translation")
introduces a warning with make htmldocs:

  ./Documentation/translations/zh_CN/mips/ingenic-tcu.rst:
    61: WARNING: Malformed table. Text in column margin in table line 6.

Adjust the table markup to address this warning.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Fixes: 419b1d4e ("doc/zh_CN: add mips ingenic-tcu.rst translation")
Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lore.kernel.org/r/20210113070023.25064-1-lukas.bulwahn@gmail.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>