hwmon: adm1021 clean ups

This patch provides some coding standard cleanups and general code improvements
(more debug info, signed values for temperatures, changed names of ADM1023
regs, removed read/write_value functions).

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Acked-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>