ACPI / processor: Fix thermal cooling device regression

The processor cooling device is no longer present for passive thermal
control.

Commit 239708a3 ("ACPI: Split out ACPI PSS from ACPI Processor driver")
moved the processing to a new function acpi_pss_perf_init(), but
missed "return 0" after successful creation.  This causes the error
handling functions to be called, which will delete the previously
created processor cooling device.

Fixes: 239708a3 (ACPI: Split out ACPI PSS from ACPI Processor driver)
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: 4.3+ <stable@vger.kernel.org> # 4.3+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>