ARM: mxc: pwm: add clk_prepare/clk_unprepare

It's for migrating to generic clk framework API.
Signed-off-by: NRichard Zhao <richard.zhao@linaro.org>
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>

arch/arm/plat-mxc/pwm.c

@@ -132,7 +132,7 @@ int pwm_enable(struct pwm_device *pwm)
 	int rc = 0;
 
 	if (!pwm->clk_enabled) {
-		rc = clk_enable(pwm->clk);
+		rc = clk_prepare_enable(pwm->clk);
 		if (!rc)
 			pwm->clk_enabled = 1;
 	}
@@ -145,7 +145,7 @@ void pwm_disable(struct pwm_device *pwm)
 	writel(0, pwm->mmio_base + MX3_PWMCR);
 
 	if (pwm->clk_enabled) {
-		clk_disable(pwm->clk);
+		clk_disable_unprepare(pwm->clk);
 		pwm->clk_enabled = 0;
 	}
 }