wifi: rtw89: coex: Add Pre-AGC control to enhance Wi-Fi RX performance

Pre-AGC(Auto gain control) is a hardware mechanism, it will auto adjust
the RX gain for every packet, it can help to keep Wi-Fi signal on a well
RX quality. The coexistence will give advice to control the API and
monitor the settings by firmware report.
Also add function to check register, these registers were monitoring
by Wi-Fi firmware and report to coexistence driver periodically. This
can help to track whether these settings were taking effect or not.

Signed-off-by: Ching-Te Ku <ku920601@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20231218061341.51255-4-pkshih@realtek.com