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>