rtw89: fix return value check in rtw89_cam_send_sec_key_cmd()

Fix the return value check which testing the wrong variable
in rtw89_cam_send_sec_key_cmd().

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: e3ec7017 ("rtw89: add Realtek 802.11ax driver")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211018033102.1813058-1-yangyingliang@huawei.com