hwmon: (lm70) fix links in doc and comments

Update links in the documentation and in-code comments which point to
the datasheet.

The current links don't work because National Semiconductor (which is the
original manufacturer of this chip) has been a part of Texas Instruments
since 2011 and http://www.national.com/ doesn't work anymore.

Fixes: e1a8e913

 ("[PATCH] lm70: New hardware monitoring driver")
Signed-off-by: Kousik Sanagavarapu <five231003@gmail.com>
Link: https://lore.kernel.org/r/20240318154540.90613-3-five231003@gmail.com


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