hwmon: (mc13783-adc) Use nxp.com URLs

Use the nxp.com URLs for the MC13783 and MC13892 datasheets.

The original URLs are still valid, but the nxp.com one is shorter
and more up-to-date.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>