ARM: mx31moboard: 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>
diff --git a/arch/arm/mach-imx/mach-mx31moboard.c b/arch/arm/mach-imx/mach-mx31moboard.c
index f225262..96e042d 100644
--- a/arch/arm/mach-imx/mach-mx31moboard.c
+++ b/arch/arm/mach-imx/mach-mx31moboard.c
@@ -507,7 +507,7 @@
 	struct clk *clk = clk_get_sys("imx2-wdt.0", NULL);
 
 	if (!IS_ERR(clk))
-		clk_enable(clk);
+		clk_prepare_enable(clk);
 
 	mxc_iomux_mode(MX31_PIN_WATCHDOG_RST__WATCHDOG_RST);