hwmon: (gl518sm) Fix checkpatch issues

hwmon: (gl518sm) Fix checkpatch issues

Fixed:
ERROR: do not use assignment in if condition
ERROR: space required after that ',' (ctx:VxV)
ERROR: spaces required around that '?' (ctx:VxE)
ERROR: spaces required around that '<' (ctx:VxV)
ERROR: spaces required around that '==' (ctx:VxV)
ERROR: spaces required around 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WARNING: simple_strtol is obsolete, use kstrtol instead
WARNING: simple_strtoul is obsolete, use kstrtoul instead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.

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