docs: driver-api: address duplicate label warning

Delete identically named subsection to fix Documentation warning:

  Documentation/driver-api/w1.rst:11: \
  WARNING: duplicate label driver-api/w1:w1 api internal to the kernel, \
  other instance in Documentation/driver-api/w1.rst

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20200330060132.7773-1-lukas.bulwahn@gmail.com


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