USB: xhci: correctly enable interrupts

xhci has its own interrupt enabling routine, which will try to
use MSI-X/MSI if present. So the usb core shouldn't try to enable
legacy interrupts; on some machines the xhci legacy IRQ setting
is invalid.

v3: Be careful to not break XHCI_BROKEN_MSI workaround (by trenn)

Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Oliver Neukum <oneukum@suse.de>
Cc: Thomas Renninger <trenn@suse.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Frederik Himpe <fhimpe@vub.ac.be>
Cc: David Haerdeman <david@hardeman.nu>
Cc: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Reviewed-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index f1f01a8..849470b 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -350,7 +350,7 @@
 	 * generate interrupts.  Don't even try to enable MSI.
 	 */
 	if (xhci->quirks & XHCI_BROKEN_MSI)
-		return 0;
+		goto legacy_irq;
 
 	/* unregister the legacy interrupt */
 	if (hcd->irq)
@@ -371,6 +371,7 @@
 		return -EINVAL;
 	}
 
+ legacy_irq:
 	/* fall back to legacy interrupt*/
 	ret = request_irq(pdev->irq, &usb_hcd_irq, IRQF_SHARED,
 			hcd->irq_descr, hcd);