[SCSI] cxgbi: get rid of gl_skb in cxgbi_ddp_info

Remove gl_skb from cxgbi_ddp_info as it is only used by cxgb3i.

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>