ath10k: add per chain RSSI reporting

ath10k: add per chain RSSI reporting

BugLink: http://bugs.launchpad.net/bugs/1706531
Report per chain RSSI to mac80211.

Signed-off-by: Norik Dzhandzhapanyan <norikd@gmail.com>
[kvalo@qca.qualcomm.com: fix conflicts and style]
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
(cherry picked from commit 8241253d03fe9098e98315a4d66027ae31ab65c5)
Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>