ezusb: decouple some nodes from ezusb-iidx-emu

This fixes a build failure in newer gcc for popnhook.
Since node-16seg has a dependency on iidxio

src/main/ezusb-emu/node.h

@@ -0,0 +1,29 @@
+#ifndef EZUSB_IIDX_EMU_NODE_H
+#define EZUSB_IIDX_EMU_NODE_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "ezusb-iidx/msg.h"
+
+/**
+ * Interface for an ezusb node
+ */
+struct ezusb_iidx_emu_node {
+    /* Addressable node id by the ezusb device */
+    const uint8_t node_id;
+
+    /* "Constructor" like init call. Called when node is added */
+    void (*init_node)(void);
+
+    /* Process an incoming command detrmined for this node */
+    uint8_t (*process_cmd)(uint8_t cmd_id, uint8_t cmd_data, uint8_t cmd_data2);
+
+    /* Bulk read data from the node */
+    bool (*read_packet)(struct ezusb_iidx_msg_bulk_packet *pkg);
+
+    /* Bulk write data to the node */
+    bool (*write_packet)(const struct ezusb_iidx_msg_bulk_packet *pkg);
+};
+
+#endif