When bdx_read_mac() fails, no error return code of bdx_probe()
is assigned.
To fix this bug, err is assigned with -EFAULT as error return code.
Reported-by: TOTE Robot <oslab@tsinghua.edu.cn> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>