Correcting changes made in dlsch_demodulation.c in 8cbe7cf6

The number of tx and rx antennas is a parameter for the dimensions of the channel estimates/rx data arrays. It should be passed, rather than hard coded, otherwise 4x4 setting is not supported.

It was replaced by the hard-coded values during the merge 8cbe7cf6, this issue brings the changes back as it was on mmse_receiver branch.