[SCSI] cxgb4i: tcp push bit fix

Fixed the parentheses so the tcp push bit would be sent properly.

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