clocksource/drivers/atmel-st: Remove useless 'status'

Fix the following coccicheck warning:

drivers/clocksource/timer-atmel-st.c:142:6-12: Unneeded variable:
"status". Return "0" on line 166

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200414120238.35704-1-yanaijie@huawei.com