tcp: remove unused parameter of tcp_sacktag_bsearch()

parameter state in the tcp_sacktag_bsearch() is not used.
So, it can be removed.

Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>