sctp: remove rcu_read_lock from sctp_bind_addr_state

sctp_bind_addr_state() is called either in packet rcv path or
by sctp_copy_local_addr_list(), which are under rcu_read_lock.
So there's no need to call it again in sctp_bind_addr_state().

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>