ACPI/PCI: pci_link: reduce verbosity when IRQ is enabled

When ACPI Link object is enabled, the message is printed with a warning
prefix. Some test tools are capturing warning and test error types as
errors. Let's reduce the verbosity of success case.

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>