pwm: Add can_sleep property to drivers

Calls to PWM drivers connected through I2C can sleep.
Use the new can_sleep property.

Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Florian Vaussard <florian.vaussard@epfl.ch>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
diff --git a/drivers/pwm/pwm-twl.c b/drivers/pwm/pwm-twl.c
index e65db95..f783efc 100644
--- a/drivers/pwm/pwm-twl.c
+++ b/drivers/pwm/pwm-twl.c
@@ -315,6 +315,7 @@
 	twl->chip.dev = &pdev->dev;
 	twl->chip.base = -1;
 	twl->chip.npwm = 2;
+	twl->chip.can_sleep = true;
 
 	mutex_init(&twl->mutex);