docs: filesystems: convert ntfs.txt to ReST

- Add a SPDX header;
- Adjust document title;
- Comment out text-only ToC;
- Some whitespace fixes and new line breaks;
- Mark literal blocks as such;
- Add table markups;
- Add it to filesystems/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/f09ca6c9bdd4e7aa7208f3dba0b8753080b38d03.1581955849.git.mchehab+huawei@kernel.org


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