rtlwifi: btcoex: 23b 2ant: adjust wifi duration for bt a2dp

The larger the bt a2dp bit pool is, the more time bt needs to receive
them. If we do not adjust the wifi duration, the voice quality will be
low. Hence we reduce the time that wifi holds, to improve the a2dp
service.

Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Pkshih <pkshih@realtek.com>
Cc: Birming Chiu <birming@realtek.com>
Cc: Shaofu <shaofu@realtek.com>
Cc: Steven Ting <steventing@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>