gpio: include consumer header in gpiolib.h

We are forward-declaring enum gpiod_flags, but this is not referenced
by pointer, it is a real struct member, so we need to actually include
it to compile anything including the local gpiolib.h header.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.h

@@ -13,13 +13,13 @@
 #define GPIOLIB_H
 
 #include <linux/gpio/driver.h>
+#include <linux/gpio/consumer.h> /* for enum gpiod_flags */
 #include <linux/err.h>
 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/cdev.h>
 
 enum of_gpio_flags;
-enum gpiod_flags;
 enum gpio_lookup_flags;
 struct acpi_device;