driver core: class: use lock_class_key already present in struct subsys_private

driver core: class: use lock_class_key already present in struct subsys_private

In commit 37e98d9bedb5 ("driver core: bus: move lock_class_key into
dynamic structure"), we moved the lock_class_key into the internal
structure shared by busses and classes, but only used it for buses.

Move the class code to use this structure as it is already present and
being allocated, instead of the statically allocated on-the-stack
variable that class_create() was using as part of a macro wrapper around
the core function call.

Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20230324100132.1633647-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>