[SCSI] qla1280: set residual correctly

Jeremy caught a bug in the qla1280 driver where it didn't set the
residual value correctly.

Signed-off-by: Jeremy Higdon <jeremy@sgi.com>
Signed-off-by: Jes Sorensen <jes@sgi.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>