wil6210: drop RX probe reponses with low SNR

FW now reports SNR for RX management frames.
Drop probe responses with SNR lower than the configured threshold.

Change-Id: Ife1863b07aebe5cb6097420290c0c10b590c2da1
Signed-off-by: Dedy Lansky <dlansky@codeaurora.org>
CRs-Fixed: 2143032
Signed-off-by: Alexei Avshalom Lazar <ailizaro@codeaurora.org>