rtw88: 8723d: Add coex support

8723D is a Wifi+BT combo card. To make them work properly, we need coex
mechanism to avoid interference, such as TX simultaneously. Basically,
coex.c provide main algorithm to deal with many use cases, and this commit
adds some parameters and ops differ from other chips, because coex
hardware and WiFi generation are changed.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200512102621.5148-8-yhchuang@realtek.com