clocksource/drivers/timer-gxp: Add missing error handling in gxp_timer_probe

Add platform_device_put() to make sure to free the platform
device in the event platform_device_add() fails.

Fixes: 5184f4bf ("clocksource/drivers/timer-gxp: Add HPE GXP Timer")
Signed-off-by: Lin Yujun <linyujun809@huawei.com>
Link: https://lore.kernel.org/r/20220914033018.97484-1-linyujun809@huawei.com


Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>