[SCSI] qla4xxx: fix up residual handling

the check in the residual case has an incorrect test of scsi_status
(the logic is reversed, it should be scsi_status != 0 instead of
!scsi_status.  Since we checked a few lines above that scsi_status was
non-zero, just eliminate this test

Signed-off-by: David C Somayajulu <david.somayajulu@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>