Assign antenna ports correctly for 1 and 2 layers for aerial.
With this change aerial successfully decodes PUSCH with 2 UL layers.
The code should use sched_pusch->dmrs.num_dmrs_cdm_grps_no_data == 1 rather
than NFAPI_MODE != NFAPI_MODE_AERIAL, but that will make the changes a bit
more extensive.
Prior to this change, sending antenna_ports.val = 2 with rank 2 would tell
the UE to transmit on DMRS ports 2,3 rather than 0,1 causing it to not decode.