fix eddystone packet header byte order

[jerryneedell]

I notice that is I set the tx power ,my app was not recognizing the URL in the Eddystone beacon.
Lookin at the spec

https://github.com/google/eddystone/tree/master/eddystone-url
I think the tx_power and url scheme fields are reversed
swapping them seems to work, my App now set the URL with a non-zero tx_power.

before , with tx_power = 0 it was still a "valid" url_scheme so it worked until tx_power was set.

reported by receiving app (IOS Locate Beacon)
before change

Tx_power - default = 0
UUID: FEAA Data: 10 03 00 61 64 61 66 72 75 2E 69 74 2F 34 30 36 32 
tx_power = -54
UUID: FEAA Data: 10 03 CA 61 64 61 66 72 75 2E 69 74 2F 34 30 36 32 

after change

UUID: FEAA Data: 10 00 03 61 64 61 66 72 75 2E 69 74 2F 34 30 36 32
tx_power = -54
UUID: FEAA Data: 10 CA 03 61 64 61 66 72 75 2E 69 74 2F 34 30 36 32 

[dhalbert]

You're right! https://github.com/google/eddystone/tree/master/eddystone-url

[dhalbert]

Thanks!