HAL_PX4: make available_memory() uint32_t

libraries/AP_HAL_PX4/Util.cpp

@@ -124,14 +124,9 @@ bool PX4Util::get_system_id(char buf[40])
 /**
    how much free memory do we have in bytes.
 */
-uint16_t PX4Util::available_memory(void) 
+uint32_t PX4Util::available_memory(void) 
 {
-    struct mallinfo mem;
-    mem = mallinfo();
-    if (mem.fordblks > 0xFFFF) {
-        return 0xFFFF;
-    }
-    return mem.fordblks;
+    return mallinfo().fordblks;
 }
 
 /*

libraries/AP_HAL_PX4/Util.h

@@ -45,7 +45,7 @@ public:
      */
     bool get_system_id(char buf[40]);
 
-    uint16_t available_memory(void);
+    uint32_t available_memory(void) override;
 
     /*
       return a stream for access to nsh shell