mptcp: move sockopt function into a new file

The MPTCP sockopt implementation is going to be much
more big and complex soon. Let's move it to a different
source file.

No functional change intended.

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>
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index d8de1e9..14f0114 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -571,6 +571,11 @@ void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk);
 void mptcp_data_ready(struct sock *sk, struct sock *ssk);
 bool mptcp_finish_join(struct sock *sk);
 bool mptcp_schedule_work(struct sock *sk);
+int mptcp_setsockopt(struct sock *sk, int level, int optname,
+		     sockptr_t optval, unsigned int optlen);
+int mptcp_getsockopt(struct sock *sk, int level, int optname,
+		     char __user *optval, int __user *option);
+
 void __mptcp_check_push(struct sock *sk, struct sock *ssk);
 void __mptcp_data_acked(struct sock *sk);
 void __mptcp_error_report(struct sock *sk);