fix eddystone packet header byte order

Author: jerryneedell

adafruit_ble/beacon.py

@@ -151,6 +151,6 @@ def __init__(self, url, tx_power=0, interval=1.0):
         adv_data.add_field(AdvertisingData.SERVICE_DATA_16_BIT_UUID,
                            b''.join((self._EDDYSTONE_ID,
                                      b'\x10',
-                                     struct.pack("<BB", url_scheme_num, tx_power),
+                                     struct.pack("<BB", tx_power, url_scheme_num),
                                      bytes(short_url, 'ascii'))))
         super().__init__(adv_data, interval)