htc: implement remaining htclow::HtclowManagerImpl funcs (mux impls pending)

libraries/libstratosphere/source/htclow/mux/htclow_mux_channel_impl.hpp

@@ -62,6 +62,10 @@ namespace ams::htclow::mux {
             void RemovePacket(const PacketHeader &header);
 
             void UpdateState();
+        public:
+            void SetSendBuffer(void *buf, size_t buf_size, size_t max_packet_size);
+            void SetReceiveBuffer(void *buf, size_t buf_size);
+            void SetSendBufferWithData(const void *buf, size_t buf_size, size_t max_packet_size);
         private:
             void ShutdownForce();
             void SetState(ChannelState state);