Fix bad trace data storage

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@1094 42af7a65-404d-4744-a932-0658087f49c3

drivers/usbdev/usbdev_trace.c

@@ -146,7 +146,7 @@ void usbtrace(uint16 event, uint16 value)
       /* Yes... save the new trace data at the head */
 
       g_trace[g_head].event = event;
-      g_trace[g_tail].event = value;
+      g_trace[g_head].value = value;
 
       /* Increment the head and (probably) the tail index */