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>