AP_HAL: add get_output_mode() and HAL_WITH_IO_MCU_DSHOT

libraries/AP_HAL/AP_HAL_Boards.h

@@ -169,6 +169,10 @@
 #define HAL_WITH_IO_MCU 0
 #endif
 
+#ifndef HAL_WITH_IO_MCU_DSHOT
+#define HAL_WITH_IO_MCU_DSHOT 0
+#endif
+
 // this is used as a general mechanism to make a 'small' build by
 // dropping little used features. We use this to allow us to keep
 // FMUv2 going for as long as possible

libraries/AP_HAL/RCOutput.h

@@ -274,6 +274,12 @@ public:
 
     virtual void    set_output_mode(uint32_t mask, enum output_mode mode) {}
 
+    virtual enum output_mode get_output_mode(uint32_t& mask) {
+      mask = 0;
+      return MODE_PWM_NORMAL;
+    }
+
+
     /*
      * get output mode banner to inform user of how outputs are configured
      */