xHCI: Correct the #define XHCI_LEGACY_DISABLE_SMI

Re-define XHCI_LEGACY_DISABLE_SMI and used it in right way. All SMI enable
bits will be cleared to zero and flag bits 29:31 are also cleared to zero.
Other bits should be presvered as Table 146.

This patch should be backported to kernels as old as 2.6.31.

Signed-off-by: Alex He <alex.he@amd.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@vger.kernel.org
diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
index 11de5f1..32dada8 100644
--- a/drivers/usb/host/pci-quirks.c
+++ b/drivers/usb/host/pci-quirks.c
@@ -825,9 +825,13 @@
 		}
 	}
 
-	/* Disable any BIOS SMIs */
-	writel(XHCI_LEGACY_DISABLE_SMI,
-			base + ext_cap_offset + XHCI_LEGACY_CONTROL_OFFSET);
+	val = readl(base + ext_cap_offset + XHCI_LEGACY_CONTROL_OFFSET);
+	/* Mask off (turn off) any enabled SMIs */
+	val &= XHCI_LEGACY_DISABLE_SMI;
+	/* Mask all SMI events bits, RW1C */
+	val |= XHCI_LEGACY_SMI_EVENTS;
+	/* Disable any BIOS SMIs and clear all SMI events*/
+	writel(val, base + ext_cap_offset + XHCI_LEGACY_CONTROL_OFFSET);
 
 	if (usb_is_intel_switchable_xhci(pdev))
 		usb_enable_xhci_ports(pdev);