Replace acpi_bus_get_device() that is going to be dropped with
acpi_fetch_acpi_dev().

No intentional functional impact.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/3173256.44csPzL39Z@kreacherSigned-off-by: Vinod Koul <vkoul@kernel.org>