[SCSI] Revert "qla2xxx: During loopdown perform Diagnostic loopback."

commit 491118df
Author: Saurav Kashyap <saurav.kashyap@qlogic.com>
Date:   Tue Aug 16 11:31:50 2011 -0700

    [SCSI] qla2xxx: During loopdown perform Diagnostic loopback.

The LOOP_DOWN test is not needed.

Signed-off-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>