made ESP32 LEDC driver selectable via build flag

Author: Richard Unger

src/drivers/hardware_specific/esp32_mcu.cpp

@@ -1,6 +1,6 @@
 #include "../hardware_api.h"
 
-#if defined(ESP_H) && defined(ARDUINO_ARCH_ESP32) && defined(SOC_MCPWM_SUPPORTED) 
+#if defined(ESP_H) && defined(ARDUINO_ARCH_ESP32) && defined(SOC_MCPWM_SUPPORTED) && !defined(SIMPLEFOC_ESP32_USELEDC)
 
 #include "driver/mcpwm.h"
 #include "soc/mcpwm_reg.h"