Use existing swap() function rather than duplicating its implementation.

./drivers/net/wireless/realtek/rtl8xxxu/core.c:6749:30-31: WARNING opportunity for swap().
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=9358Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20240619024017.53246-1-jiapeng.chong@linux.alibaba.com