Documentation: fix ref to trace stm content

Signed-off-by: NTom Saeger <tom.saeger@oracle.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/trace/intel_th.txt

@@ -37,7 +37,7 @@ description is at Documentation/ABI/testing/sysfs-bus-intel_th-devices-gth.
 
 STH registers an stm class device, through which it provides interface
 to userspace and kernelspace software trace sources. See
-Documentation/tracing/stm.txt for more information on that.
+Documentation/trace/stm.txt for more information on that.
 
 MSU can be configured to collect trace data into a system memory
 buffer, which can later on be read from its device nodes via read() or