AP_HAL: correct include ordering in srxl.h

The header needs stdint.h which it was only getting because it was
included after stdint.h in the cpp file.

Stop including standard headers before other ArduPilot headers

libraries/AP_HAL/utility/srxl.cpp

@@ -20,13 +20,13 @@
    - 2016.10.23: SRXL variant V1 sucessfully (Testbench and Pixhawk/MissionPlanner) tested with RX-9-DR M-LINK (SW v1.26)
  */
 
+#include "srxl.h"
+
+#include <AP_Math/crc.h>
+
 #include <stdio.h>
 #include <stdint.h>
 #include <string.h>
-#include <AP_Math/crc.h>
-#include "srxl.h"
-
-
 
 /* SRXL datastream characteristics for all variants */
 #define SRXL_MIN_FRAMESPACE_US 8000U    /* Minumum space between srxl frames in us (applies to all variants)  */

libraries/AP_HAL/utility/srxl.h

@@ -19,6 +19,8 @@
 
 #pragma once
 
+#include <stdint.h>
+
 /*
  * Decoder for SRXL protocol
  *