rtlwifi: btcoexist: 23b 1ant: fix duplicated code for different branches

A typo led to this issue, which was detected with the help of Coccinelle.

In addition to fixing the error, the code is refactored to eliminate an
if statement.

Addresses-Coverity-ID: 1226788

Reported-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Ping-Ke Shih <pkshih@realtek.com>
Cc: Yan-Hsuan Chuang <yhchuang@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>