pwm: zx: Add missing cleanup in error path

zx_pwm_probe() called clk_prepare_enable() before; this must be undone
in the error path.

Fixes: 4836193c ("pwm: Add ZTE ZX PWM device driver")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/pwm-zx.c

@@ -236,6 +236,7 @@ static int zx_pwm_probe(struct platform_device *pdev)
 	ret = pwmchip_add(&zpc->chip);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
+		clk_disable_unprepare(zpc->pclk);
 		return ret;
 	}