Revert "pinctrl: consumer: use correct retval for placeholder functions"

This reverts commit 5a7d2efd.

As per discussion on the mailing list, this is not the right
thing to do. NULL cookies are valid in the stubs.
Reported-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

include/linux/pinctrl/consumer.h

@@ -82,7 +82,7 @@ static inline int pinctrl_gpio_direction_output(unsigned gpio)
 
 static inline struct pinctrl * __must_check pinctrl_get(struct device *dev)
 {
-	return ERR_PTR(-ENOSYS);
+	return NULL;
 }
 
 static inline void pinctrl_put(struct pinctrl *p)
@@ -93,7 +93,7 @@ static inline struct pinctrl_state * __must_check pinctrl_lookup_state(
 							struct pinctrl *p,
 							const char *name)
 {
-	return ERR_PTR(-ENOSYS);
+	return NULL;
 }
 
 static inline int pinctrl_select_state(struct pinctrl *p,
@@ -104,7 +104,7 @@ static inline int pinctrl_select_state(struct pinctrl *p,
 
 static inline struct pinctrl * __must_check devm_pinctrl_get(struct device *dev)
 {
-	return ERR_PTR(-ENOSYS);
+	return NULL;
 }
 
 static inline void devm_pinctrl_put(struct pinctrl *p)