ACPI: LPSS: Use ACPI_COMPANION() directly

The ACPI_HANDLE() macro returns the ACPI handle of the ACPI device
object returned by the ACPI_COMPANION() macro, so it is more
straightforward to call the latter directly instead of passing
the handle produced by the former to acpi_bus_get_device().

Modify the code accordingly (no intentional functional impact).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>