rtw88: coex: add debug message

Add message for debugging usage and the program flow is no change.
Add a variable reserved for WLAN firmware synchronize.
Add a group of variable to save BT packet counter, it will be
assigned as mechanism judgment in the future. Now it is just for
debug usage.

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/20201126021059.11981-3-pkshih@realtek.com