tcp: remove unneeded code from tcp_stream_alloc_skb()

Aligning @size argument to 4 bytes is not needed.

The header alignment has nothing to do with @size.

It really depends on skb->head alignment and MAX_TCP_HEADER.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>