docs: fix nested numbering in the TOC

With Sphinx 1.6 nested numbering is reported as warning::

  ./input/joydev/index.rst:13: WARNING: input/joydev/joystick-api is already assigned section numbers (nested numbered toctree?)
  ./media/uapi/cec/cec-funcs.rst:8: WARNING: media/uapi/cec/cec-func-open is already assigned section numbers (nested numbered toctree?)
  ./media/uapi/cec/cec-funcs.rst:8: WARNING: media/uapi/cec/cec-func-close is already assigned section numbers (nested numbered toctree?)
  ./media/uapi/cec/cec-funcs.rst:8: WARNING: media/uapi/cec/cec-func-ioctl is already assigned section numbers (nested numbered toctree?)
  ./media/uapi/cec/cec-funcs.rst:8: WARNING: media/uapi/cec/cec-func-poll is already assigned section numbers (nested numbered toctree?)
  ./media/uapi/cec/cec-funcs.rst:8: WARNING: media/uapi/cec/cec-ioc-adap-g-caps is already assigned section numbers (nested numbered toctree?)
  ./media/uapi/cec/cec-funcs.rst:8: WARNING: media/uapi/cec/cec-ioc-adap-g-log-addrs is already assigned section numbers (nested numbered toctree?)
  ./media/uapi/cec/cec-funcs.rst:8: WARNING: media/uapi/cec/cec-ioc-adap-g-phys-addr is already assigned section numbers (nested numbered toctree?)
  ./media/uapi/cec/cec-funcs.rst:8: WARNING: media/uapi/cec/cec-ioc-dqevent is already assigned section numbers (nested numbered toctree?)
  ./media/uapi/cec/cec-funcs.rst:8: WARNING: media/uapi/cec/cec-ioc-g-mode is already assigned section numbers (nested numbered toctree?)
  ./media/uapi/cec/cec-funcs.rst:8: WARNING: media/uapi/cec/cec-ioc-receive is already assigned section numbers (nested numbered toctree?)

TOC numbering is already set in::

  ./input/devices/index.rst:9:
  ./media/uapi/cec/cec-api.rst:19:

I guess the nested numbering in:

  ./input/joydev/index.rst
  ./media/uapi/cec/cec-funcs.rst

is just a C&P typo, so lets remove it.

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>