ACPI / scan: More straightforward preparation of ACPI device objects

Simplify the code preparing struct acpi_device objects for
registration by removing useless code, moving different pieces of
code into the functions they belong to and making a couple of int
functions always returning 0 void.

This also fixes a possible memory leak in ACPI device registration
error code path by making acpi_device_register() detach data from
device->handle if device_register() fails and prepares the scanning
code for special-casing ACPI power resources (next patch).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>