clocksource/drivers/clps711x: Make clps711x_clksrc_init() static

Fix sparse warning:

drivers/clocksource/clps711x-timer.c:96:13: warning:
 symbol 'clps711x_clksrc_init' was not declared. Should it be static?

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <daniel.lezcano@linaro.org>
Cc: <shc_work@mail.ru>
Cc: <linux-arm-kernel@lists.infradead.org>
Link: https://lkml.kernel.org/r/20190322143708.12716-1-yuehaibing@huawei.com