ArduSub: clear RC overrides on forward/lateral/yaw/vertical input

Override has_pilot_input_for_override_clear() to use Sub's joystick
axes (forward, lateral, yaw, plus throttle mapped to vertical thrust)
instead of the Copter-style roll/pitch/yaw/throttle set.

ArduSub/RC_Channel_Sub.cpp

@@ -52,6 +52,20 @@ bool RC_Channels_Sub::has_valid_input() const
     return RC_Channels::has_valid_input();
 }
 
+bool RC_Channels_Sub::has_pilot_input_for_override_clear()
+{
+    if (channel_outside_trim_dz(get_forward_channel()) ||
+        channel_outside_trim_dz(get_lateral_channel()) ||
+        channel_outside_trim_dz(get_yaw_channel())) {
+        return true;
+    }
+    // Sub throttle (=vertical) is biased away from trim by the GCS, so use movement-since-override-start
+    if (throttle_moved_since_override_start()) {
+        return true;
+    }
+    return false;
+}
+
 
 // do_aux_function - implement the function invoked by auxiliary switches
 bool RC_Channel_Sub::do_aux_function(const AuxFuncTrigger &trigger)

ArduSub/RC_Channel_Sub.h

@@ -26,6 +26,9 @@ public:
     bool in_rc_failsafe() const override;
     // returns true if throttle arming checks should be run
     bool arming_check_throttle() const override;
+
+    bool has_pilot_input_for_override_clear() override;
+
     RC_Channel_Sub obj_channels[NUM_RC_CHANNELS];
     RC_Channel_Sub *channel(const uint8_t chan) override {
         if (chan >= ARRAY_SIZE(obj_channels)) {