wifi: rtw89: coex: modify LNA2 setting to avoid BT destroyed Wi-Fi aggregation

To prevent LNA2 change its gain during a Wi-Fi aggregation packet while
GNT_BT pull high. Otherwise, changes of this gain will destroy the whole
aggregation when Wi-Fi RX.

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://lore.kernel.org/r/20220920010939.12173-7-pkshih@realtek.com