fixes the overflow issue in the PUCCH2 RX with 4+ RX antennas and 12+
bits (polar code format). The fix scales the polar decoding LLR
computation according to the number of RX antennas. The issue was clear
for 100 MHz 4 RX antennas. Even

  nr_pucchsim -s -5 -q 8 -P 2 -b 12 -R 273 -z4 -n1000

doesn't converge to 0 BLER with increasing SNR. The issue didn't appear
in CI because of the bandwidth and antenna count limitations.