[SCSI] SCSI core: better initialization for sdev->scsi_level

This patch will affect the CDB in INQUIRY commands sent to LUNs above 0 
when LUN-0 reports a scsi_level of 0; the LUN bits will no longer be set 
in the second byte of the CDB.  This is as it should be.  Nevertheless, 
it's possible that some wacky device might be adversely affected.  I doubt 
anyone will complain...

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>