wl18xx: add radar detection implementation

Add support for CAC start/stop commands, and pass
radar detection events from the fw to mac80211.

Bump fw name (to wl18xx-fw-4.bin) and min fw version
(to 8.9.*.*.11), and align event mailbox accordingly.

Signed-off-by: Guy Mishol <guym@ti.com>
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>