scsi: libsas: Use pr_fmt(fmt)

In preparation for dropping the libsas printk wrappers, use pr_fmt(fmt)
declaration to add the framework log prefix - "sas".

Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>