[SCSI] zfcp: consolidate sysfs things into one file.

zfcp was using three files to deal with sysfs representation
for adapters, ports and units. The consolidation into one file
prevents code-duplication and eases maintainability.

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@HansenPartnership.com>