pwm: vt8500: Undo preparation of a clock source.

Undo preparation of a clock source if vt8500_pwm_probe() is not
successful.
Signed-off-by: NArvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: NThierry Reding <thierry.reding@gmail.com>

drivers/pwm/pwm-vt8500.c

@@ -241,6 +241,7 @@ static int vt8500_pwm_probe(struct platform_device *pdev)
 	ret = pwmchip_add(&chip->chip);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "failed to add PWM chip\n");
+		clk_unprepare(chip->clk);
 		return ret;
 	}