tcp: Rearrange tests in inet_csk_bind_conflict().

The following patch adds code in the !inet_use_bhash2_on_bind(sk)
case in inet_csk_bind_conflict().

To avoid adding nest and make the change cleaner, this patch
rearranges tests in inet_csk_bind_conflict().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>