According to the schematics user button should be on `PD5` not `PC5`
(so `GPIO_PIN(3, 5)`).
Due to the super high values resistors being used for the external
pullup it seems if you use a internal pullup it doesn't work.
The Sub-GHz Antenna of the Openmote-B is always connected to the AT86RF215.
It is the 2.4 GHz radial that can be switched between the CC2538 and the AT86RF215.
This changes the name of the defines accordingly.
