hwmon: (lm90) Add support for 2nd remote channel's offset register

The ADT7481 have LM90_HAVE_TEMP3 and LM90_HAVE_OFFSET flags, but the
support of second remote channel's offset is missing. Add that
implementation.

Signed-off-by: Slawomir Stepien <slawomir.stepien@nokia.com>
Link: https://lore.kernel.org/r/20220607063504.1287855-2-sst@poczta.fm


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