ARM: mxs: convert platform code to clk_prepare/clk_unprepare

The patch converts mxs platform code to clk_prepare/clk_unprepare
by using helper functions clk_prepare_enable/clk_disable_unprepare.

Signed-off-by: Richard Zhao <richard.zhao@linaro.org>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/mach-mxs/mach-mx28evk.c b/arch/arm/mach-mxs/mach-mx28evk.c
index 064ec5a..6b9e83e 100644
--- a/arch/arm/mach-mxs/mach-mx28evk.c
+++ b/arch/arm/mach-mxs/mach-mx28evk.c
@@ -228,7 +228,7 @@
 	/* Enable fec phy clock */
 	clk = clk_get_sys("pll2", NULL);
 	if (!IS_ERR(clk))
-		clk_enable(clk);
+		clk_prepare_enable(clk);
 
 	/* Power up fec phy */
 	ret = gpio_request(MX28EVK_FEC_PHY_POWER, "fec-phy-power");