scripts/tags.sh: Add magic for trace-events

Make tags find the trace-event definitions

Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1290591835.2072.438.camel@laptop>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>