[SCSI] qla2xxx: Cover UNDERRUN case where SCSI status is set.

Currently, if target sets the SCSI Status (with Check condition)
and there is no FCP residual bit set then driver  does not check
for dropped frame.  This could lead to data corruption.

Signed-off-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>