Fix UE resource element extraction bug for subframes 0,5,6
This issue addresses the resource element extraction for subframes 0,5,6 which contain PSS/SSS/PBCH resource elements. The UE receiver improperly computed the number of allocatde resource blocks in the symbols containing these physical control channels (there are two separate bugs which affect odd-PRB cell configurations in one case and even-PRB cell configurations in the other). It has to do with computing the number of allocated PRBs per symbol which was done wrong in dlsch_extract_rbs_single() in openair1/PHY/LTE_TRANSPORT/dlsch_demodulation.c (nb_rb which is returned by the function) and affected the LLR generation in dlsch_qpsk_llr, dlsch_16qam_llr and dlsch_64qam_llr. The second bug (for SISO only) was that dlsch_extract_rbs_single() didn't skip the PBCH/PSS/SSS resource elements at all for channels with an even number of PRBs. This was clearly bad but never noticed since we only tested the UE with 10/20 MHz in TM2 with commercial eNBs where the problem was at the time. It was not done for TM1 configurations.