On 64 bit systems we write past the end of the arg[] array.

Fixes: 8e84c258 ('wcn36xx: mac80211 driver for Qualcomm WCN3660/WCN3680 hardware')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>