[SCSI] zfcp: Remove unused payload field from zfcp_dbf_san_record

Remove the unused payload field from the struct zfcp_dbf_san_record,
saving some space in the SAN trace.

Reviewed-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>