bladerf: tentative to have it functional
Several problems are present. The first is that _write returns 0 instead of the number of samples. We solve it by returning nsamps. The second is that _read may return less samples at the beginning and we don't want to exit for that. We solve it also by returning nsamps. (We still need to log more in this, to be done in the next commit.) The third is that after initialization we don't send anything for a while, time for the softmodem to finish its init. This generates lots of "RX overrun". We solve it by disabling TX and RX modules after init and then in trx_brf_start we activate them again (and also call bladerf_sync_config, which seems to be mandatory, and bladerf_calibrate_dc, which may be avoided, perhaps). Maybe not the end of the story. Sometimes it works, UE connects, traffic is fine (tested only with 5MHz). Sometimes it does not, UE does not connect, or it connects but then traffic is bad, especially uplink. To be refined.