scsi: iscsi: Adjust iface sysfs attr detection

ISCSI_NET_PARAM_IFACE_ENABLE belongs to enum iscsi_net_param instead of
iscsi_iface_param so move it to ISCSI_NET_PARAM. Otherwise, when we call
into the driver, we might not match and return that we don't want attr
visible in sysfs. Found in code review.

Link: https://lore.kernel.org/r/20210901085336.2264295-1-libaokun1@huawei.com
Fixes: e746f345

 ("scsi: iscsi: Fix iface sysfs attr detection")
Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>