xhci: Avoid BUG() in interrupt context

Change the BUGs in xhci_find_new_dequeue_state() to WARN_ONs, to avoid
bringing down the box if one of them is hit

This patch should be queued for stable kernels back to 2.6.31.
Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@kernel.org

drivers/usb/host/xhci-ring.c

@@ -474,8 +474,11 @@ void xhci_find_new_dequeue_state(struct xhci_hcd *xhci,
 	state->new_deq_seg = find_trb_seg(cur_td->start_seg,
 			dev->eps[ep_index].stopped_trb,
 			&state->new_cycle_state);
-	if (!state->new_deq_seg)
-		BUG();
+	if (!state->new_deq_seg) {
+		WARN_ON(1);
+		return;
+	}
+
 	/* Dig out the cycle state saved by the xHC during the stop ep cmd */
 	xhci_dbg(xhci, "Finding endpoint context\n");
 	ep_ctx = xhci_get_ep_ctx(xhci, dev->out_ctx, ep_index);
@@ -486,8 +489,10 @@ void xhci_find_new_dequeue_state(struct xhci_hcd *xhci,
 	state->new_deq_seg = find_trb_seg(state->new_deq_seg,
 			state->new_deq_ptr,
 			&state->new_cycle_state);
-	if (!state->new_deq_seg)
-		BUG();
+	if (!state->new_deq_seg) {
+		WARN_ON(1);
+		return;
+	}
 
 	trb = &state->new_deq_ptr->generic;
 	if ((trb->field[3] & TRB_TYPE_BITMASK) == TRB_TYPE(TRB_LINK) &&