rtlwifi: btcoex: 21a 2ant: limit rx aggregation size to avoid bt interrupt

Larger packets have higher opportunity to be interrupt by bt signal.
In order to shorten the transmission time, control the packet
aggregation size.

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>