examples: include endian.h for be16toh and le16toh declarations

this gets exposed on musl, on glibc endian.h gets pulled in indirectly

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

examples/c/i2c_mpu6050.c

@@ -27,6 +27,7 @@
  */
 
 /* standard headers */
+#include <endian.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>

examples/c/iio.c

@@ -28,6 +28,7 @@
 /* standard headers */
 #include <stdlib.h>
 #include <unistd.h>
+#include <endian.h>
 
 /* mraa header */
 #include "mraa/iio.h"