iio: Add missing include guards to headers

Add include guards to the IIO headers where they are missing. This avoids
compile errors due to redefined types if a file is included more than once.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

include/linux/iio/kfifo_buf.h

@@ -1,3 +1,5 @@
+#ifndef __LINUX_IIO_KFIFO_BUF_H__
+#define __LINUX_IIO_KFIFO_BUF_H__
 
 #include <linux/kfifo.h>
 #include <linux/iio/iio.h>
@@ -6,3 +8,4 @@
 struct iio_buffer *iio_kfifo_allocate(struct iio_dev *indio_dev);
 void iio_kfifo_free(struct iio_buffer *r);
 
+#endif

include/linux/iio/machine.h

@@ -8,6 +8,9 @@
  * the Free Software Foundation.
  */
 
+#ifndef __LINUX_IIO_MACHINE_H__
+#define __LINUX_IIO_MACHINE_H__
+
 /**
  * struct iio_map - description of link between consumer and device channels
  * @adc_channel_label:	Label used to identify the channel on the provider.
@@ -22,3 +25,5 @@ struct iio_map {
 	const char *consumer_dev_name;
 	const char *consumer_channel;
 };
+
+#endif

include/linux/iio/trigger_consumer.h

@@ -7,6 +7,9 @@
  * the Free Software Foundation.
  */
 
+#ifndef __LINUX_IIO_TRIGGER_CONSUMER_H__
+#define __LINUX_IIO_TRIGGER_CONSUMER_H__
+
 /**
  * struct iio_poll_func - poll function pair
  *
@@ -50,3 +53,5 @@ void iio_trigger_notify_done(struct iio_trigger *trig);
  */
 int iio_triggered_buffer_postenable(struct iio_dev *indio_dev);
 int iio_triggered_buffer_predisable(struct iio_dev *indio_dev);
+
+#endif