trace-events: fix first line comment in trace-events

Documentation is docs/tracing.txt instead of docs/trace-events.txt.

find . -name trace-events -exec \
     sed -i "s?See docs/trace-events.txt for syntax documentation.?See docs/tracing.txt for syntax documentation.?" \
     {} \;

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Message-id: 1470669081-17860-1-git-send-email-lvivier@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

linux-user/trace-events

@@ -1,4 +1,4 @@
-# See docs/trace-events.txt for syntax documentation.
+# See docs/tracing.txt for syntax documentation.
 
 # linux-user/signal.c
 user_setup_frame(void *env, uint64_t frame_addr) "env=%p frame_addr=%"PRIx64