ACPI: scan: Add acpi_dev_get_next_consumer_dev()

In commit b83e2b30 ("ACPI: scan: Add function to fetch dependent
of ACPI device") we added a means of fetching the first device to
declare itself dependent on another ACPI device in the _DEP method.
One assumption in that patch was that there would only be a single
consuming device, but this has not held.

Replace that function with a new function that fetches the next consumer
of a supplier device. Where no "previous" consumer is passed in, it
behaves identically to the original function.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Daniel Scally <djrscally@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>