tracing: Fix return while holding a lock in register_tracer()

tracing: Fix return while holding a lock in register_tracer()

commit 81f295d7b807 ("tracing: Make tracer_flags use the right set_flag
callback")  introduces a potential mutex deadlock issue, as it forgets to
free the mutex when allocaing the tracer_flags gets fail.

The issue was found by Dan Carpenter through Smatch static code check tool.

Link: http://lkml.kernel.org/r/1457958941-30265-1-git-send-email-chuhu@redhat.com
Fixes: 81f295d7b807 ("tracing: Make tracer_flags use the right set_flag callback")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Chunyu Hu <chuhu@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>