PCI/ACPI: Clarify message about _OSC failure

PCI/ACPI: Clarify message about _OSC failure

This message:

  acpi PNP0A08:02: _OSC failed (AE_NOT_FOUND); disabling ASPM

is alarming and slightly misleading.  Per the PCI Firmware Spec, r3.2, sec
4.5.1, _OSC is required for PCIe hierarchies.  If _OSC is absent or fails,
the OS must not attempt to use any of the features defined for _OSC.  That
includes native hotplug, native PME, AER, and other things as well as ASPM.

Rephrase the message to:

  acpi PNP0A08:02: _OSC: platform retains control of PCIe features (AE_NOT_FOUND)

Previous discussion at https://lore.kernel.org/r/20200602223618.GA845676@bjorn-Precision-5520/

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Sinan Kaya <okaya@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Yicong Yang <yangyicong@hisilicon.com>