staging: iio: Add #include guards to header files

This patch adds #include guards in order to make the header files idempotent.

Signed-off-by: Roberta Dobrescu <roberta.dobrescu@gmail.com>
Acked-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/iio/iio_dummy_evgen.h

@@ -1,2 +1,7 @@
+#ifndef _IIO_DUMMY_EVGEN_H_
+#define _IIO_DUMMY_EVGEN_H_
+
 int iio_dummy_evgen_get_irq(void);
 int iio_dummy_evgen_release_irq(int irq);
+
+#endif /* _IIO_DUMMY_EVGEN_H_ */

drivers/staging/iio/iio_simple_dummy.h

@@ -8,6 +8,8 @@
  * Join together the various functionality of iio_simple_dummy driver
  */
 
+#ifndef _IIO_SIMPLE_DUMMY_H_
+#define _IIO_SIMPLE_DUMMY_H_
 #include <linux/kernel.h>
 
 struct iio_dummy_accel_calibscale;
@@ -117,4 +119,6 @@ static inline int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev,
 static inline
 void iio_simple_dummy_unconfigure_buffer(struct iio_dev *indio_dev)
 {};
+
 #endif /* CONFIG_IIO_SIMPLE_DUMMY_BUFFER */
+#endif /* _IIO_SIMPLE_DUMMY_H_ */

drivers/staging/iio/ring_hw.h

@@ -9,6 +9,9 @@
  *
  */
 
+#ifndef _RING_HW_H_
+#define _RING_HW_H_
+
 /**
  * struct iio_hw_ring_buffer- hardware ring buffer
  * @buf:	generic ring buffer elements
@@ -20,3 +23,5 @@ struct iio_hw_buffer {
 };
 
 #define iio_to_hw_buf(r) container_of(r, struct iio_hw_buffer, buf)
+
+#endif /* _RING_HW_H_ */