ACPI / PM: Drop pm_message_t argument from device suspend callback

None of the drivers implementing the ACPI device suspend callback
uses the pm_message_t argument of it, so this argument may be dropped
entirely from that callback.  This will simplify switching the ACPI
bus type to PM handling based on struct dev_pm_ops.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>