iio:trigger_consumer.h: Add missing includes and forward declarations

Add includes and forward declarations for types used in this file. This avoids
compile errors if the other files have not been included before.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

include/linux/iio/trigger_consumer.h

@@ -10,6 +10,12 @@
 #ifndef __LINUX_IIO_TRIGGER_CONSUMER_H__
 #define __LINUX_IIO_TRIGGER_CONSUMER_H__
 
+#include <linux/interrupt.h>
+#include <linux/types.h>
+
+struct iio_dev;
+struct iio_trigger;
+
 /**
  * struct iio_poll_func - poll function pair
  *