AP_HAL_VRBrain: Remove GPIO::analogPinToDigitalPin()

libraries/AP_HAL_VRBRAIN/GPIO.cpp

@@ -84,12 +84,6 @@ void VRBRAINGPIO::pinMode(uint8_t pin, uint8_t output)
     }
 }
 
-int8_t VRBRAINGPIO::analogPinToDigitalPin(uint8_t pin)
-{
-    return -1;
-}
-
-
 uint8_t VRBRAINGPIO::read(uint8_t pin) {
     switch (pin) {
 

libraries/AP_HAL_VRBRAIN/GPIO.h

@@ -23,7 +23,6 @@ public:
 	VRBRAINGPIO();
     void    init() override;
     void    pinMode(uint8_t pin, uint8_t output) override;
-    int8_t  analogPinToDigitalPin(uint8_t pin) override;
     uint8_t read(uint8_t pin) override;
     void    write(uint8_t pin, uint8_t value) override;
     void    toggle(uint8_t pin) override;