ACPI: scan: Adjust white space in acpi_device_add()

Add empty lines in some places in acpi_device_add() to help
readability and drop leading spaces before the labels in there.

No functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>