watchdog imx2: prepare clk before enabling it

Signed-off-by: Sascha Hauer <[e-mail]>

drivers/watchdog/imx2_wdt.c

···
 {
 	if (!test_and_set_bit(IMX2_WDT_STATUS_STARTED, &imx2_wdt.status)) {
 		/* at our first start we enable clock and do initialisations */
-		clk_enable(imx2_wdt.clk);
+		clk_prepare_enable(imx2_wdt.clk);
 
 		imx2_wdt_setup();
 	} else	/* delete the timer that pings the watchdog after close */