HAL_PX4: added px4_param stub functions

this replaces the PX4 parameter system with stub functions that fail
all parameter find calls

libraries/AP_HAL_PX4/px4_param.cpp

@@ -0,0 +1,35 @@
+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+/*
+  This replaces the PX4Firmware parameter system with dummy
+  functions. The ArduPilot parameter system uses different formatting
+  for FRAM and we need to ensure that the PX4 parameter system doesn't
+  try to access FRAM in an invalid manner
+ */
+
+#include <px4_defines.h>
+#include <px4_posix.h>
+#include <stdio.h>
+
+#include "systemlib/param/param.h"
+
+#include "uORB/uORB.h"
+#include "uORB/topics/parameter_update.h"
+
+/** parameter update topic */
+ORB_DEFINE(parameter_update, struct parameter_update_s);
+
+param_t param_find(const char *name)
+{
+    ::printf("PX4: param_find(%s)\n", name);
+    return PARAM_INVALID;
+}
+
+int param_get(param_t param, void *val)
+{
+    return -1;
+}
+
+int param_set(param_t param, const void *val)
+{
+    return -1;
+}