scsi: hisi_sas: Directly return when running I_T_nexus reset if phy disabled

At hisi_sas_debug_I_T_nexus_reset(), we call sas_phy_reset() to reset a
phy. But if the phy is disabled, sas_phy_reset() will directly return
-ENODEV without issue a phy reset request.

If so, We can directly return -ENODEV to libsas before issue a phy
reset.

Link: https://lore.kernel.org/r/1567774537-20003-4-git-send-email-john.garry@huawei.com
Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>