hwmon: Add submitting-patches checklist to documentation

When writing hardware monitoring drivers, there are some common pitfalls which
keep coming up in code reviews. This patch provides a document describing all
those pitfalls and how to avoid them.

Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Acked-by: Jean Delvare <khali@linux-fr.org>