clocksource/drivers/cadence_ttc: Fix memory leak in ttc_setup_clockevent()

If clk_notifier_register() failed, ttc_setup_clockevent() will return
without freeing 'ttcce', which will leak memory.

Fixes: 70504f31

 ("clocksource/drivers/cadence_ttc: Convert init function to return error")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20201116135123.2164033-1-yukuai3@huawei.com