Add newline when formatting SAS transport class phy 'enable' attribute.

[root@localhost ~]# cat /sys/devices/pci0000:00/0000:00:0d.0/0000:0f:00.0/host3/phy-3:2/sas_phy/phy-3:2/enable
1[root@localhost ~]#

Link: https://lore.kernel.org/r/1594975472-12486-1-git-send-email-wangxiongfeng2@huawei.comReviewed-by: John Garry <john.garry@huawei.com>
Reviewed-by: Bart van Assche <bvanassche@acm.org>
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>