USB: fix mistake in usb_hcd_giveback_urb

This patch (as971) fixes a small mistake: The URB's completion status
needs to be adjusted before the URB is passed to usmon_urb_complete(),
not afterward.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>