ACPI/PCI: PCIe ASPM _OSC support capabilities called when root bridge added

The _OSC capabilities OSC_ACTIVE_STATE_PWR_SUPPORT and
OSC_CLOCK_PWR_CAPABILITY_SUPPORT are set when the root bridge is added
with pci_acpi_osc_support(), so we no longer need to do it in the ASPM
driver.  Also add the function pcie_aspm_enabled, which returns true if
pcie_aspm=off is not on the kernel command-line.

Signed-off-by: Andrew Patterson <andrew.patterson@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 96e68e8..9fe026b 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -347,6 +347,9 @@
 	/* Indicate support for various _OSC capabilities. */
 	if (pci_ext_cfg_avail(root->bus->self))
 		flags |= OSC_EXT_PCI_CONFIG_SUPPORT;
+	if (pcie_aspm_enabled())
+		flags |= OSC_ACTIVE_STATE_PWR_SUPPORT |
+			OSC_CLOCK_PWR_CAPABILITY_SUPPORT;
 	if (flags != base_flags)
 		pci_acpi_osc_support(device->handle, flags);