docs: hwmon: pxe1610: convert to ReST format and add to the index

This document was recently introduced. Convert it to ReST
just like the other hwmon documents, adding it to the hwmon index.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Link: https://lore.kernel.org/r/657bf022625e0888d3becf10c78d162eeb864608.1563792334.git.mchehab+samsung@kernel.org


Signed-off-by: Guenter Roeck <linux@roeck-us.net>