Make read-only globals const, additional fixes

- Global variables that are never written to are marked const
- Remove some EXTERN declaration
- Remove unused `log_mem_multi` from logging module

executables/nr-softmodem.c

@@ -138,16 +138,10 @@ static int tx_max_power[MAX_NUM_CCs]; /* =  {0,0}*/;
 
 int chain_offset=0;
 
-
 uint8_t dci_Format = 0;
-uint8_t agregation_Level =0xFF;
-
 uint8_t nb_antenna_tx = 1;
 uint8_t nb_antenna_rx = 1;
 
-char ref[128] = "internal";
-char channels[128] = "0";
-
 int rx_input_level_dBm;
 
 int otg_enabled;