A0 pin number can be changed in the variants (#4778)

Author: acosinwork

variants/generic/common.h

@@ -47,7 +47,9 @@ static const uint8_t MOSI  = PIN_SPI_MOSI;
 static const uint8_t MISO  = PIN_SPI_MISO;
 static const uint8_t SCK   = PIN_SPI_SCK;
 
+#ifndef PIN_A0
 #define PIN_A0 (17)
+#endif /* PIN_A0 */
 
 static const uint8_t A0 = PIN_A0;