pwm: atmel: set pwm_chip can_sleep flag

atmel_pwm_config() calls clk_get_rate() which might sleep, so we need to
set pwm_chip can_sleep flag.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/pwm-atmel.c

@@ -357,6 +357,7 @@ static int atmel_pwm_probe(struct platform_device *pdev)
 
 	atmel_pwm->chip.base = -1;
 	atmel_pwm->chip.npwm = 4;
+	atmel_pwm->chip.can_sleep = true;
 	atmel_pwm->config = data->config;
 
 	ret = pwmchip_add(&atmel_pwm->chip);