wifi: rtw89: coex: show connecting state in debug message

The variable cnt_connecting is to indicate if we are connecting to an AP.
This is an important clue for coexistence to assign more time slot to WiFi
side in this situation to ensure WiFi can establish connection.

Without this patch, compiler warns:
  drivers/net/wireless/realtek/rtw89/coex.c:3244:25: warning: variable
    'cnt_connecting' set but not used [-Wunused-but-set-variable]

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220912021009.6011-1-pkshih@realtek.com