scsi: scsi_transport_sas: Fix error handling in sas_phy_add()

If transport_add_device() fails in sas_phy_add(), the kernel will crash
trying to delete the device in transport_remove_device() called from
sas_remove_host().

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000108
CPU: 61 PID: 42829 Comm: rmmod Kdump: loaded Tainted: G        W          6.1.0-rc1+ #173
pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : device_del+0x54/0x3d0
lr : device_del+0x37c/0x3d0
Call trace:
 device_del+0x54/0x3d0
 attribute_container_class_device_del+0x28/0x38
 transport_remove_classdev+0x6c/0x80
 attribute_container_device_trigger+0x108/0x110
 transport_remove_device+0x28/0x38
 sas_phy_delete+0x30/0x60 [scsi_transport_sas]
 do_sas_phy_delete+0x6c/0x80 [scsi_transport_sas]
 device_for_each_child+0x68/0xb0
 sas_remove_children+0x40/0x50 [scsi_transport_sas]
 sas_remove_host+0x20/0x38 [scsi_transport_sas]
 hisi_sas_remove+0x40/0x68 [hisi_sas_main]
 hisi_sas_v2_remove+0x20/0x30 [hisi_sas_v2_hw]
 platform_remove+0x2c/0x60

Fix this by checking and handling return value of transport_add_device()
in sas_phy_add().

Fixes: c7ebbbce

 ("[SCSI] SAS transport class")
Suggested-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20221107124828.115557-1-yangyingliang@huawei.com
Reviewed-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>