AP_HAL: AnalogIn: add missing include

Since we are using uint8_t and uint16_t types we need to include the
correspondent system header. Otherwise it would depend on the include
order of who is including this particular header, causing failures as we
move headers around.

libraries/AP_HAL/AnalogIn.h

@@ -2,6 +2,8 @@
 #ifndef __AP_HAL_ANALOG_IN_H__
 #define __AP_HAL_ANALOG_IN_H__
 
+#include <inttypes.h>
+
 #include "AP_HAL_Namespace.h"
 
 class AP_HAL::AnalogSource {