docs: hwmon: Add an index file and rename docs to *.rst

Now that all files were converted to ReST format, rename them
and add an index.

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

include/linux/platform_data/ds620.h

@@ -14,7 +14,7 @@ struct ds620_platform_data {
 	 *  1 = PO_LOW
 	 *  2 = PO_HIGH
 	 *
-	 * (see Documentation/hwmon/ds620)
+	 * (see Documentation/hwmon/ds620.rst)
 	 */
 	int pomode;
 };