rtw88: coex: remove unnecessary feature/function

Because the WLAN RSSI report feature had been implemented at WLAN link info
update function, it is redundant to update WLAN RSSI while BT is updating
link info, so remove the update WLAN RSSI part.

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/20201112031430.4846-3-pkshih@realtek.com