driver core: class: make class_for_each_device() options const

class_for_each_device() does not modify the struct class or the struct
device passed into it, so mark them as const * to enforce that.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Link: https://lore.kernel.org/r/20230313181843.1207845-6-gregkh@linuxfoundation.org


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