scsi: megaraid_sas: use octal permissions instead of constants

Checkpatch emits a warning when using symbolic permissions. Use octal
permissions instead.  No functional change.

Signed-off-by: Tomas Henzl <thenzl@redhat.com>
Acked-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>