scsi: mpt3sas: Fix sparse warnings

1) Used variable __le64/__le32 whichever required in building NVME
PRP, and passed to LE Controller.

2) Remove unused functions, And Declared functions as static which are
used only in mpt3sas_scsih.c.

Signed-off-by: Chaitra P B <chaitra.basappa@broadcom.com>
Signed-off-by: Suganath Prabu S <suganath-prabu.subramani@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>