rtw88: coex: remove unnecessary WLAN slot extend

Remove extend 5 ms related operation at WLAN media status notify.
The mechanism should be enable only while DUT connect to a AP that it
doesn't follow our power save control or its rate is decreasing unusually
sensitive. So we extend a extra slot to save the transmission rate.

The original logic will always extend WLAN slot.
It will lead to BT slot always decrease 5 ms.

Remove write scoreboard action at WLAN media status notify.
It has already done in WLAN info notify.

Signed-off-by: Ching-Te Ku <ku920601@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201112031430.4846-11-pkshih@realtek.com