Transceiver: Move nbits burst size calculation to pullRadioVector()

That's where all the filling logic happens, while in driveReceiveFIFO we
mostly want to take the burst, generate a message and sent it over the
socket.

Related: OS#4006
Change-Id: Ib1df10c40d737954904290f57d58b1c77d65f82e
2 files changed