bugfix: fix sync for oaisim
With the current implementation of oaisim (rxdata and channel simulation), we cannot call trx_read_func on a dummy buffer. The code will actually modify the rxdata buffers of the UE. This is has to be rewritten properly. In the meantime, let's introduce a simple hack. The idea of the read at this point is to wait for the synch to finish and not lose samples from the hardware in the real UE. In the simulator, as it is today, we can simply sleep until the synch code has finished its work.