The macro to_subsys_private() needs to switch to using
container_of_const() as it turned out to being incorrectly casting a
const pointer to a non-const one.  Make this change and fix up the one
offending user to be correctly handling a const pointer properly.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20230111093327.3955063-1-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>