mptcp: Remove unused inline function mptcp_rcv_synsent()

commit 263e120 ("mptcp: consolidate synack processing.")
left behind this, remove it.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/mptcp.h

@@ -164,10 +164,6 @@ static inline bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 	return false;
 }
 
-static inline void mptcp_rcv_synsent(struct sock *sk)
-{
-}
-
 static inline bool mptcp_synack_options(const struct request_sock *req,
 					unsigned int *size,
 					struct mptcp_out_options *opts)