trace_kprobes: Fix memory leak

tp->nr_args is not set before we "goto error",
it causes memory leak for free_trace_probe() use tp->nr_args
to free memory of args.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B0CEB95.2060107@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>