scsi: libsas: Move sas_add_parent_port() to sas_expander.c

Move sas_add_parent_port() to sas_expander.c and rename it to
sas_ex_add_parent_port() as it is only used in this file.

Signed-off-by: Xingui Yang <yangxingui@huawei.com>
Link: https://lore.kernel.org/r/20240312141103.31358-3-yangxingui@huawei.com


Reviewed-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>