[SCSI] qla2xxx: Additional residual-count corrections during UNDERRUN handling.

Add additional tightening of residual-count handling (originally
from commit 6acf8190) where the
driver should discard any lower SCSI-status during
firmware/transport residual-count mismatches.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>