wifi: rtlwifi: Use min()/max() to improve code

Use min()/max() to reduce the code and improve its readability.

Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250715121721.266713-8-rongqianfeng@vivo.com