hwmon: (adm1021) Fix checkpatch issues

Fixed:
ERROR: do not use assignment in if condition
WARNING: simple_strtol is obsolete, use kstrtol instead
WARNING: space prohibited between function name and open parenthesis '('

Modify multi-line comments to follow Documentation/CodingStyle.

Cc: Michael Abbott <michael.abbott@diamond.ac.uk>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>