[SCSI] correct the sym2 period setting routines

There's a slight bug in the routines in that if the period requires dt,
then the routine will unconditionally set it.  DT may only be set if
Wide is also set, so this turns back on the wide bit.

For domain validation to work correctly, we need to observe the wide bit
absolutely.

Acked by: Matthew Wilcox <willy@debian.org>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>