clocksource/drivers: Rename clocksource_probe to timer_probe

The function name is now renamed to 'timer_probe' for consistency with
the CLOCKSOURCE_OF_DECLARE => TIMER_OF_DECLARE change.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>