ARM: mxc: epit: add clk_prepare/clk_unprepare

It's for migrating to generic clk framework API.
Signed-off-by: Richard Zhao <richard.zhao@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/plat-mxc/epit.c

@@ -203,7 +203,7 @@ static int __init epit_clockevent_init(struct clk *timer_clk)
 
 void __init epit_timer_init(struct clk *timer_clk, void __iomem *base, int irq)
 {
-	clk_enable(timer_clk);
+	clk_prepare_enable(timer_clk);
 
 	timer_base = base;