rtlwifi: btcoex: 23b 2ant: turn off antenna when rssi is too high/low

For 2-antenna combo card, the signal of the neighbor antenna could be
over noise level and cause be severe interference. So we monitor the
rssi and turn off one of the antennas when the other is transmitting
and the rssi level is beyond a threshold.

Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Pkshih <pkshih@realtek.com>
Cc: Birming Chiu <birming@realtek.com>
Cc: Shaofu <shaofu@realtek.com>
Cc: Steven Ting <steventing@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>