[SCSI] zfcp: introduce _setup, _destroy for qdio and FC

Extract independent data structures and introduce common _setup and
_destroy routines for QDIO and Fibre Channel related data structures

Signed-off-by: Swen Schillig <swen@vnet.ibm.com>
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>