Add CSC message for sending ADC values across the bus

sw/airborne/csc/csc_msg_def.h

@@ -5,6 +5,7 @@
 #define CSC_MOTOR_CMD_ID    1
 #define CSC_MOTOR_STATUS_ID 2
 #define CSC_BOARD_STATUS_ID 3
+#define CSC_BOARD_ADCVOLTS_ID 4
 
 /* Received from the autopilot */
 struct CscServoCmd {
@@ -26,4 +27,9 @@ struct CscStatusMsg {
   uint32_t msg_count;
 } __attribute__((packed));
 
+struct CscADCMsg {
+  float ADCVolts1;
+  float ADCVolts2;
+} __attribute__((packed));
+
 #endif