Make turning off unused power resources (after the enumeration of
devices and during system-wide resume from S3) more straightforward
by using the observation that the power resource state stored in
struct acpi_power_resource can be used to determine whether or not
the give power resource has any users.

Namely, when the state of the power resource is unknown, its _STA
method has never been evaluated (or the evaluation of it has failed)
and its _ON and _OFF methods have never been executed (or they have
failed to execute), so for all practical purposes it can be assumed
to have no users (or to be unusable).  Therefore, instead of checking
the number of power resource users, it is sufficient to check if its
state is known.

Moreover, if the last known state of a given power resource is "off",
it is not necessary to turn it off, because it has been used to
initialize the power state or the wakeup power resources list of at
least one device and either its _STA method has returned 0 ("off"),
or its _OFF method has been successfully executed already.

Accordingly, modify acpi_turn_off_unused_power_resources() to do the
above checks (which are suitable for both uses of it) instead of
using the number of power resource users or evaluating its _STA
method, drop its argument (which is not useful any more) and update
its callers.

Also drop the users field from struct acpi_power_resource as it is
not useful any more.
Tested-by: Dave Olsthoorn <dave@bewaar.me>
Tested-by: Shujun Wang <wsj20369@163.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>