AP_HAL_ChibiOS: add Link Quality reporting to RC protocols

libraries/AP_HAL_ChibiOS/RCInput.cpp

@@ -180,6 +180,7 @@ void RCInput::_timer_tick(void)
         _num_channels = MIN(_num_channels, RC_INPUT_MAX_CHANNELS);
         rcprot.read(_rc_values, _num_channels);
         _rssi = rcprot.get_RSSI();
+        _rx_link_quality = rcprot.get_rx_link_quality();
 #ifndef HAL_NO_UARTDRIVER
         rc_protocol = rcprot.protocol_name();
 #endif

libraries/AP_HAL_ChibiOS/RCInput.h

@@ -52,7 +52,9 @@ public:
     int16_t get_rssi(void) override {
         return _rssi;
     }
-
+    int16_t get_rx_link_quality(void) override {
+        return _rx_link_quality;
+    }
     const char *protocol() const override { return last_protocol; }
 
     void _timer_tick(void);
@@ -65,6 +67,7 @@ private:
     uint8_t _num_channels;
     Semaphore rcin_mutex;
     int16_t _rssi = -1;
+    int16_t _rx_link_quality = -1;
     uint32_t _rcin_timestamp_last_signal;
     bool _init;
     const char *last_protocol;