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/5790600.lOV4Wx5bFT@kreacherSigned-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>