pwm: Add missing static storage class specifiers in core.c file

Fixes the following sparse warnings:
drivers/pwm/core.c:152:6: warning:
symbol 'of_pwmchip_add' was not declared. Should it be static?
drivers/pwm/core.c:165:6: warning:
symbol 'of_pwmchip_remove' was not declared. Should it be static?
Signed-off-by: NSachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: NThierry Reding <thierry.reding@avionic-design.de>

drivers/pwm/core.c

@@ -149,7 +149,7 @@ static struct pwm_device *of_pwm_simple_xlate(struct pwm_chip *pc,
 	return pwm;
 }
 
-void of_pwmchip_add(struct pwm_chip *chip)
+static void of_pwmchip_add(struct pwm_chip *chip)
 {
 	if (!chip->dev || !chip->dev->of_node)
 		return;
@@ -162,7 +162,7 @@ void of_pwmchip_add(struct pwm_chip *chip)
 	of_node_get(chip->dev->of_node);
 }
 
-void of_pwmchip_remove(struct pwm_chip *chip)
+static void of_pwmchip_remove(struct pwm_chip *chip)
 {
 	if (chip->dev && chip->dev->of_node)
 		of_node_put(chip->dev->of_node);