docs/zh_CN: Fix malformed table

Running "make htmldocs" generates the following build error
in zh_CN/cpu-freq/cpu-drivers.rst:

Documentation/translations/zh_CN/cpu-freq/cpu-drivers.rst:109: ERROR: Malformed table.

Fix the table formatting to resolve the error.

Signed-off-by: Gopi Krishna Menon <krishnagopi487@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>