leds: fix unsigned value overflow in atmel pwm driver

Fix an unsigned value overflow in the error handling code in the
Atmel PWM driver.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>

drivers/leds/leds-atmel-pwm.c

@@ -37,7 +37,7 @@ static int __init pwmled_probe(struct platform_device *pdev)
 {
 	const struct gpio_led_platform_data	*pdata;
 	struct pwmled				*leds;
-	unsigned				i;
+	int					i;
 	int					status;
 
 	pdata = pdev->dev.platform_data;