isci: remove base_port abstraction

Merge struct sci_base_port into scic_sds_port.  Until now sci_base_port
was referenced indirectly with scic_sds_port->parent field.

'sci_base_port' state machine handlers were also incorporated into
scic_sds_port handlers.

Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Maciej Trela <Maciej.Trela@intel.com>
Signed-off-by: Maciej Patelczyk <maciej.patelczyk@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>