ARM: mxs: retrieve timer irq from device tree

Rather than using the static timer irq definition, we should retrieve
timer irq from device tree for better.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

drivers/clk/mxs/clk-imx28.c

@@ -337,7 +337,7 @@ int __init mx28_clocks_init(void)
 	for (i = 0; i < ARRAY_SIZE(clks_init_on); i++)
 		clk_prepare_enable(clks[clks_init_on[i]]);
 
-	mxs_timer_init(MX28_INT_TIMER0);
+	mxs_timer_init();
 
 	return 0;
 }