net, scsi/csgb4i: convert skb->transport_header into skb_transport_header(skb)

The change set of 1a37e412, "net: Use 16bits for *_headers fields
of struct skbuff" converted from sk_buff_data_t into 16bit integer.
So skb->tail needs to be converted to skb_tail_pointer(skb).

Found by inspection. Compile tested only.

Cc: Simon Horman <horms@verge.net.au>
Cc: Li RongQing <roy.qing.li@gmail.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Acked-by: Simon Horman <horms@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>