scsi_debug: bump inquiry version to SPC-4, update version descriptors

Since a lot of functionality from SPC-4 is supported by this
driver (e.g. LBP and PI) then bump the default INQUIRY version
from SPC-3 to SPC-4. Also update the INQUIRY version
descriptors.

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>