Documentation/SubmittingDrivers: convert it to ReST markup

- Change the document title markup to make it on a higher level;
- Add blank lines as needed, to improve the output;
- use italics for the country-code at kernel.org ftp URL.

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