docs: networking: device drivers: convert aquantia/atlantic.txt to ReST

- add SPDX header;
- use copyright symbol;
- adjust title and its markup;
- comment out text-only TOC from html/pdf output;
- mark code blocks and literals as such;
- adjust identation, whitespaces and blank lines where needed;
- add to networking/index.rst.

Signed-off-by: Mauro Carvalho Chehab <[email protected]>
Signed-off-by: David S. Miller <[email protected]>