Update ESP32 definition in PlatformIO (espressif#217)

Author: me-no-dev

configs/pio_end.txt

@@ -1,5 +1,5 @@
         "ARDUINO_ARCH_ESP32",
-        "ESP32",
+        ("ESP32", "ESP32"),
         ("F_CPU", "$BOARD_F_CPU"),
         ("ARDUINO", 10812),
         ("ARDUINO_VARIANT", '\\"%s\\"' % board_config.get("build.variant").replace('"', "")),