scsi: libsas: Set port when ex_phy is added or deleted

We found that when ex_phy was attached and added to the parent wide port,
ex_phy->port was not set, resulting in sas_unregister_devs_sas_addr() not
calling sas_port_delete_phy() when deleting the phy, and the deleted phy
was still on the parent wide port's phy_list.

When we use sas_port_add_ex_phy() to set ex_phy->port to solve the above
problem, we find that after all the phys of the parent_port are removed and
the number of phy becomes 0, the parent_port will not be set to NULL.  This
causes the freed parent port to be used when attaching a new ex_phy in
sas_ex_add_parent_port().

Use sas_port_add_ex_phy() instead of sas_port_add_phy() to set ex_phy->port
when ex_phy is added to the parent port, and set ex_dev->parent_port to
NULL when the number of phy on the port becomes 0.

Signed-off-by: Xingui Yang <yangxingui@huawei.com>
Link: https://lore.kernel.org/r/20240312141103.31358-4-yangxingui@huawei.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>