ata_sas_port_init() now only contains a single initialization.

Move this single initialization to ata_sas_port_alloc(), since:
1) ata_sas_port_alloc() already initializes some of the struct members.
2) ata_sas_port_alloc() is only used by libsas.
Suggested-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>