iio:consumer.h: Fix include guard

The symbol name for the #ifndef and the #define of the include guard do not
match and thus it becomes quite ineffective. Add the missing '_' to fix this.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

include/linux/iio/consumer.h

@@ -8,7 +8,7 @@
  * the Free Software Foundation.
  */
 #ifndef _IIO_INKERN_CONSUMER_H_
-#define _IIO_INKERN_CONSUMER_H
+#define _IIO_INKERN_CONSUMER_H_
 #include <linux/iio/types.h>
 
 struct iio_dev;