usb-uhci: fix irq handling on error.

Spec on UHCI_STS_USBERR: "If the TD on which the error interrupt
occurred also had its IOC bit set, both this bit and Bit 0 are set."

Make UHCI emulation do that.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb-uhci.c

@@ -730,6 +730,9 @@ out:
         td->ctrl |= TD_CTRL_STALL;
         td->ctrl &= ~TD_CTRL_ACTIVE;
         s->status |= UHCI_STS_USBERR;
+        if (td->ctrl & TD_CTRL_IOC) {
+            *int_mask |= 0x01;
+        }
         uhci_update_irq(s);
         return 1;
 
@@ -737,6 +740,9 @@ out:
         td->ctrl |= TD_CTRL_BABBLE | TD_CTRL_STALL;
         td->ctrl &= ~TD_CTRL_ACTIVE;
         s->status |= UHCI_STS_USBERR;
+        if (td->ctrl & TD_CTRL_IOC) {
+            *int_mask |= 0x01;
+        }
         uhci_update_irq(s);
         /* frame interrupted */
         return -1;