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/2828205.e9J7NaK4W3@kreacherSigned-off-by: Takashi Iwai <tiwai@suse.de>