pinctrl: Forward declare struct device

pinctrl/devinfo.h is using forward declaration from pinctrl/consumer.h
for configurations with CONFIG_PINCTRL defined, however nothing declares
it in the opposite case. Fix this by adding a forward declaration.
Signed-off-by: Ladislav Michl <ladis@linux-mips.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

include/linux/pinctrl/devinfo.h

@@ -43,6 +43,8 @@ extern int pinctrl_init_done(struct device *dev);
 
 #else
 
+struct device;
+
 /* Stubs if we're not using pinctrl */
 
 static inline int pinctrl_bind_pins(struct device *dev)