[SCSI] cxgb3i: zero out reserved or un-used fields.

Zero out the reserved or un-used CPL message fields to prevent any garbage
value.

Signed-off-by: Karen Xie <kxie@chelsio.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>