uavcan include cstdint for fixed width integer types

src/drivers/uavcan/sensors/gnss.cpp

@@ -40,6 +40,9 @@
  */
 
 #include "gnss.hpp"
+
+#include <cstdint>
+
 #include <drivers/drv_hrt.h>
 #include <systemlib/err.h>
 #include <mathlib/mathlib.h>