rtw88: coex: add function to avoid cck lock

Some AP will not follow the power save request, or it cannot stop
transmission until its queue is empty. It may bring the decreasing of
data rate.

WLAN firmware will count is the AP still leaked packet after power save
handshake was done or not to enable WLAN slot extend mechanism.

The extend WLAN slot mechanism will extend the WLAN slot after power save
handshake, 5 ms per times, maximum is 5 times to received the leaked packet
to avoid the rate lower down.

And if the transmission was already locked at CCK rate.
The extended WLAN slot can also increase the opportunity that we can
received the CCK's long packet and be released from CCK rate.

While BT multi-link status was finished, there is possible that it still
has some packet remained for seconds. Add a timer to remain the multi-link
mechanism to protect WLAN 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@codeaurora.org>
Link: https://lore.kernel.org/r/20201126021059.11981-8-pkshih@realtek.com