PCI/ASPM: Don't touch ASPM if forcibly disabled

Don't allocate and track PCIe ASPM state when "pcie_aspm=off" is specified
on the kernel command line.

Based-on-patch-from: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: David Bulkow <david.bulkow@stratus.com>
Acked-by: Myron Stowe <myron.stowe@redhat.com>

drivers/pci/pcie/aspm.c

@@ -556,6 +556,9 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
 	struct pcie_link_state *link;
 	int blacklist = !!pcie_aspm_sanity_check(pdev);
 
+	if (!aspm_support_enabled)
+		return;
+
 	if (!pci_is_pcie(pdev) || pdev->link_state)
 		return;
 	if (pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT &&