rtw89: coex: Add case for scan offload

Turn off coexistence driver control, let firmware can control the
traffic during scan. This prevents potential unexpected behavior of
the BT driver.

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/20220401055043.12512-4-pkshih@realtek.com