register_module_notifier() returns zero in the success case.
So fix the inverted fail case check in trace events modules
handler.

[ Impact: fix spurious warning on ftrace initialization]
Reported-by: NLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: NMing Lei <tom.leiming@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>