ACPI / processor: Fix the return value of acpi_processor_ids_walk()

ACPI driver should make sure all the processor IDs in their ACPI Namespace
are unique. the driver performs a depth-first walk of the namespace tree
and calls the acpi_processor_ids_walk() to check the duplicate IDs.

But, the acpi_processor_ids_walk() mistakes the return value. If a
processor is checked, it returns true which causes the walk break
immediately, and other processors will never be checked.

Repace the value with AE_OK which is the standard acpi_status value.
And don't abort the namespace walk even on error.

Fixes: 8c8cb30f (acpi/processor: Implement DEVICE operator for processor enumeration)
Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>