scsi: lpfc: Rework lpfc_fdmi_cmd() routine for cleanup and consistency

Switch case logics are reworked so they appear more similar and
consistent. This eliminates compiler errors indicating unaligned pointer
values and packed members.

Added comments to explain previous size offset accumulations.

Link: https://lore.kernel.org/r/20220911221505.117655-10-jsmart2021@gmail.com


Co-developed-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>