driver core: class: remove struct module owner out of struct class

The module owner field for a struct class was never actually used, so
remove it as it is not doing anything at all.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Link: https://lore.kernel.org/r/20230313181843.1207845-3-gregkh@linuxfoundation.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>