hwmon: (lm87) Fix checkpatch issues

Fixed:
ERROR: do not use assignment in if condition
ERROR: space required after that close brace '}'
ERROR: space required after that ',' (ctx:VxV)
ERROR: spaces required around that '<' (ctx:VxV)
ERROR: trailing statements should be on next line
WARNING: line over 80 characters
WARNING: simple_strtol is obsolete, use kstrtol instead
WARNING: simple_strtoul is obsolete, use kstrtoul instead

Modify multi-line comments to follow Documentation/CodingStyle.

Not fixed everywhere (code complexity):
ERROR: do not use assignment in if condition

As a side effect of the changes made, attribute set functions now return an
error if an attempt is made to write non-numeric values. Previously, such
writes were interpreted as writing 0.

Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Jean Delvare <khali@linux-fr.org>