scsi: mpt3sas: use DEVICE_ATTR_{RO, RW}

Use existing macros.  No functional change.

[mkp: typo]

Signed-off-by: Tomas Henzl <thenzl@redhat.com>
Acked-by: Suganath Prabu <suganath-prabu.subramani@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>