ACPI / battery: Correctly serialise with the pending async probe

async_synchronize_cookie() only serialises all tasks up to the specified
cookie, and importantly does not wait for the task corresponding with
the cookie. [This is so that it can be trivially used from inside the
async_func_t in order to serialise with all preceding tasks.] In order
to serialise with acpi_battery_init_async() we need to compensate and
pass in the next cookie instead.

The impact today is zero since performing an async_schedule() from inside
a module init function will trigger an async_synchronize_full() prior to
the module loader's completion. However, if the probe was moved to its
own unregistered async_domain, then the async_synchronize_cookie would
be replaced with an async_synchronize_full_domain.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>