docs: hwmon: wm831x, wm8350: convert to ReST format

Convert wm831x and wm8350 to ReST format, in order to allow
them to be parsed by Sphinx.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>