Currently target_if_cp_stats_extract_vdev_summary_stats
function prints bcn SNR which can be RSSI as well based on
whether firmware supports reporting rssi or not.
Add check for firware support to print RSSI/SNR
Change-Id: Ifef7bfad7d79c1a1bb84641bc1d3632f6d683252
CRs-Fixed: 3209907