usb: don't wait if dying

[Jacob Meuser]

ok?

-- 
jake...@sdf.lonestar.org
SDF Public Access UNIX System - http://sdf.lonestar.org

Index: usb_subr.c
===================================================================
RCS file: /cvs/src/sys/dev/usb/usb_subr.c,v
retrieving revision 1.75
diff -u -p usb_subr.c
--- usb_subr.c  6 Dec 2010 04:30:57 -0000       1.75
+++ usb_subr.c  14 Dec 2010 16:16:32 -0000
@@ -351,6 +351,9 @@ usb_delay_ms(usbd_bus_handle bus, u_int ms)
 void
 usbd_delay_ms(usbd_device_handle dev, u_int ms)
 {
+       if (usbd_is_dying(dev))
+               return;
+
        usb_delay_ms(dev->bus, ms);
 }