mptcp: drop duplicate mptcp_setsockopt() declaration

commit 78962489 ("mptcp: add skeleton to sync msk socket
options to subflows") introduced a duplicate declaration of
mptcp_setsockopt(), just drop it.
Reported-by: Florian Westphal <fw@strlen.de>
Fixes: 78962489 ("mptcp: add skeleton to sync msk socket options to subflows")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/protocol.h

@@ -762,9 +762,6 @@ unsigned int mptcp_pm_get_add_addr_accept_max(struct mptcp_sock *msk);
 unsigned int mptcp_pm_get_subflows_max(struct mptcp_sock *msk);
 unsigned int mptcp_pm_get_local_addr_max(struct mptcp_sock *msk);
 
-int mptcp_setsockopt(struct sock *sk, int level, int optname,
-		     sockptr_t optval, unsigned int optlen);
-
 void mptcp_sockopt_sync(struct mptcp_sock *msk, struct sock *ssk);
 void mptcp_sockopt_sync_all(struct mptcp_sock *msk);