[SCSI] nsp_cs: time_out reaches -1

With a postfix decrement timeouts will reach -1 rather than 0, so the
errors do not appear.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>