AP_BLHeli: check for rcout serial support

don't build AP_BLHeli on HALs that can't support serial output to ESCs

libraries/AP_BLHeli/AP_BLHeli.cpp

@@ -20,6 +20,9 @@
  */
 
 #include "AP_BLHeli.h"
+
+#if HAL_SUPPORT_RCOUT_SERIAL
+
 #include <AP_Math/crc.h>
 #include <AP_Motors/AP_Motors_Class.h>
 #include <GCS_MAVLink/GCS_MAVLink.h>
@@ -1114,3 +1117,13 @@ void AP_BLHeli::update(void)
     }
     debug("ESC: mapped %u motors with mask 0x%04x", num_motors, mask);
 }
+
+/*
+  update BLHeli telemetry handling
+  This is called on push() in SRV_Channels
+ */
+void AP_BLHeli::update_telemetry(void)
+{
+}
+
+#endif // HAL_SUPPORT_RCOUT_SERIAL

libraries/AP_BLHeli/AP_BLHeli.h

@@ -23,6 +23,9 @@
 
 #include <AP_Common/AP_Common.h>
 #include <AP_HAL/AP_HAL.h>
+
+#if HAL_SUPPORT_RCOUT_SERIAL
+
 #include <AP_Param/AP_Param.h>
 #include "msp_protocol.h"
 #include "blheli_4way_protocol.h"
@@ -33,6 +36,7 @@ public:
     AP_BLHeli();
     
     void update(void);
+    void update_telemetry(void);
     bool process_input(uint8_t b);
 
     static const struct AP_Param::GroupInfo var_info[];
@@ -216,3 +220,5 @@ private:
 #ifndef UDID_START
 #define UDID_START	0x1FFF7A10
 #endif
+
+#endif // HAL_SUPPORT_RCOUT_SERIAL