scsi: mpt3sas: use list_splice_init()

Use 'list_splice_init()' instead of hand-crafted function.  No
functional change.

Signed-off-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Suganath Prabu S <suganath-prabu.subramani@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>