PCI: Allow pcie_aspm=force even when FADT indicates it is unsupported

Right now using pcie_aspm=force will not enable ASPM if the FADT indicates
ASPM is unsupported.  However, the semantics of force should probably allow
for this, especially as they did before 3c076351c4 ("PCI: Rework ASPM
disable code")

This patch just skips the clearing of any ASPM setup that the firmware has
carried out on this bus if pcie_aspm=force is being used.

Reference: http://bugs.launchpad.net/bugs/962038
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index b52630b..8474b6a 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -771,6 +771,9 @@
 {
 	struct pci_dev *child;
 
+	if (aspm_force)
+		return;
+
 	/*
 	 * Clear any ASPM setup that the firmware has carried out on this bus
 	 */