ARM: OMAP: MUSB: prevent recursive spinlock in TX path

If a hard IRQ occurs during the soft IRQ TX processing, a recursive
spinlock BUG can occur.

Prevent this by interrupt-off locking around usb_hcd_link_urb_to_ep()

Found while testing bluetooth A2DP audio over USB.
Signed-off-by: Kevin Hilman <khilman@mvista.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

drivers/usb/musb/musb_host.c

@@ -1757,7 +1757,9 @@ static int musb_urb_enqueue(
 	if (!is_host_active(musb) || !musb->is_active)
 		return -ENODEV;
 
+	spin_lock_irqsave(&musb->lock, flags);
 	ret = usb_hcd_link_urb_to_ep(hcd, urb);
+	spin_unlock_irqrestore(&musb->lock, flags);
 	if (ret)
 		return ret;