doc/zh_CN: mips: use doc references instead

doc/zh_CN: mips: use doc references instead

The Chinese mips translations refer to non-existing labels in the original
documentation. Hence, make htmldocs warns about those undefined labels on
all files in ./Documentation/translations/zh_CN/mips/.

Replace the references to non-existing labels with suitable doc references.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Fixes: 419b1d4ed1cb ("doc/zh_CN: add mips ingenic-tcu.rst translation")
Fixes: 72bc9d08868d ("doc/zh_CN: add mips features.rst translation")
Fixes: 7fd3954b0c52 ("doc/zh_CN: add mips booting.rst translation")
Fixes: b8e724fd7117 ("doc/zh_CN: add mips index.rst translation")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lore.kernel.org/r/20210113070557.28792-1-lukas.bulwahn@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>