wil6210: support FW RSSI reporting

New FW supports reporting RSSI signal in dBm.
Report RSSI to kernel in case FW has this capability.

Change-Id: I85fdae2e92a38cfb7ab9a5f97dcf363add51b959
Signed-off-by: Dedy Lansky <qca_dlansky@qca.qualcomm.com>
Signed-off-by: Maya Erez <qca_merez@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
Git-commit: 30868f5d4413759ba82c0703290f2483402fea39
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git


Signed-off-by: Maya Erez <merez@codeaurora.org>