hwmon: (lm90) Add support for the LM99 16 degree offset

The LM99 differs from the LM86, LM89 and LM90 in that it reports
remote temperatures (temp2) 16 degrees lower than they really are. So
far we have been cheating and handled this in userspace but it really
should be handled by the driver directly.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>