staging: iio: quell asprintf() warning, missing #includes

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/staging/iio/Documentation/iio_utils.h b/drivers/staging/iio/Documentation/iio_utils.h
index 9c7a5aa..c0448b3 100644
--- a/drivers/staging/iio/Documentation/iio_utils.h
+++ b/drivers/staging/iio/Documentation/iio_utils.h
@@ -13,6 +13,7 @@
 #include <stdio.h>
 #include <stdint.h>
 #include <dirent.h>
+#include <errno.h>
 
 /* Made up value to limit allocation sizes */
 #define IIO_MAX_NAME_LENGTH 30