trace_kprobes: Always show group name

Sometimes the group name is not "kprobes",
It'll be better if we can read it from tracing/kprobe_events.

 # echo 'r:laijs/vfs_read vfs_read %ax' > kprobe_events
 # cat kprobe_events
 r:laijs/vfs_read vfs_read %ax=%ax

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: <4B0CEBAF.6000104@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace_kprobe.c

@@ -760,7 +760,7 @@ static int probes_seq_show(struct seq_file *m, void *v)
 	char buf[MAX_ARGSTR_LEN + 1];
 
 	seq_printf(m, "%c", probe_is_return(tp) ? 'r' : 'p');
-	seq_printf(m, ":%s", tp->call.name);
+	seq_printf(m, ":%s/%s", tp->call.system, tp->call.name);
 
 	if (tp->symbol)
 		seq_printf(m, " %s+%u", probe_symbol(tp), tp->rp.kp.offset);