scsi: zfcp: group sort internal structure definitions for proximity

Have structures just before the structures that use them (without
disrupting sequences of using structures such as zfcp_unit and
zfcp_scsi_dev):

 - zfcp_adapter_mempool embedded in zfcp_adapter,

 - zfcp_latenc... embedded in zfcp_scsi_dev.

Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>