this_cpu_ops.txt: standardize document format

this_cpu_ops.txt: standardize document format

Each text file under Documentation follows a different
format. Some doesn't even have titles!

Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx:
- promote document title one level;
- mark literal blocks;
- move authorship to the beginning of the file and use markups.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>