scsi: hisi_sas: fix spelling mistake "digial" -> "digital"

There is a spelling mistake in literal string. Fix it.

Link: https://lore.kernel.org/r/20190916091706.32268-1-colin.king@canonical.com


Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>