PCI / pci-label: release allocated ACPI object on error recovery path

Function dsm_get_label() leaks the returned ACPI object if
obj->package.count is not 2, so fix the possible memory leak.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>