mlx5: Return -EFAULT instead of -EPERM

For copy_to/from_user() failure, the correct error code is -EFAULT not
-EPERM.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>