dlsim bugfixes

dlsim has several issues:

• missed DCIs can bias result for low SNR
• missed DCIs handling has bugs
• retransmissions are never decoded (this is also true for dlsim_tm4)
• dlsim tests fail

Todo list

• reintroduce option to run w/o PDCCH/DCI and fix corresponding error counters
• the return value (error code) of rx_pdsch should be checked
• argument -c (num_pdcch_symbols) is not respected and overwritten!
• fix dlsch_channel_level for all BWs
• add tests for 20MHz
• dlsim returns -1 if test fail
• problem with retransmissions for DCI format 2

this branch will try to fix these bugs and also re-introduce the option of running dlsim without pdcch/dci decoding