rtlwifi: btcoex: fix if == else warning

Fix the following coccicheck warning:

drivers/net/wireless/realtek/rtlwifi/btcoexist/halbtc8821a1ant.c:1604:2-4:
WARNING: possible condition with no effect (if == else).

Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220425031725.5808-1-guozhengkui@vivo.com