perf tools: Fix tracing_path_mount proper path

If there's no tracefs (RHEL7) support the tracing_path_mount
returns debugfs path which results in following fail:

# perf probe sys_write
kprobe_events file does not exist - please rebuild kernel with CONFIG_KPROBE_EVENTS.
Error: Failed to add events.

In tracing_path_debugfs_mount function we need to return the
'tracing' path instead of just the mount to make it work:

# perf probe sys_write
Added new event:
probe:sys_write (on sys_write)

You can now use it in all perf tools, such as:

perf record -e probe:sys_write -aR sleep 1

Adding the 'return tracing_path;' also to tracing_path_tracefs_mount
function just for consistency with tracing_path_debugfs_mount.

Upstream keeps working, because it has the tracefs support.

Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Jiri Olsa <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Michael Petlan <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Steven Rostedt <[e-mail]>
Fixes: 23773ca18b39 ("perf tools: Make perf aware of tracefs")
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/lib/api/fs/tracing_path.c

···
 
 	__tracing_path_set("", mnt);
 
-	return mnt;
+	return tracing_path;
 }
 
 static const char *tracing_path_debugfs_mount(void)
···
 
 	__tracing_path_set("tracing/", mnt);
 
-	return mnt;
+	return tracing_path;
 }
 
 const char *tracing_path_mount(void)