ARM: integrator: use clk_prepare_enable() for timer

The Integrator timer is using the clock framework to get the
timer frequency, but missed to prepare the clock before enabling.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/mach-integrator/integrator_ap.c

@@ -456,7 +456,7 @@ static void __init ap_init_timer(void)
 
 	clk = clk_get_sys("ap_timer", NULL);
 	BUG_ON(IS_ERR(clk));
-	clk_enable(clk);
+	clk_prepare_enable(clk);
 	rate = clk_get_rate(clk);
 
 	writel(0, TIMER0_VA_BASE + TIMER_CTRL);