hwmon: (gl518sm) Various cleanups

* Drop history, it doesn't belong there
* Drop unused struct member
* Drop bogus struct member comment
* Drop unused driver ID
* Rename new_client to client
* Drop redundant initializations to 0
* Drop useless cast
* Drop trailing space
* Fix comment
* Drop duplicate comment

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>