Expose API for hardware unique ID (#16869)

platforms/avr/hardware_id.c

@@ -0,0 +1,13 @@
+// Copyright 2022 QMK
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <avr/boot.h>
+#include "hardware_id.h"
+
+hardware_id_t get_hardware_id(void) {
+    hardware_id_t id = {0};
+    for (uint8_t i = 0; i < 10; i += 1) {
+        ((uint8_t*)&id)[i] = boot_signature_byte_get(i + 0x0E);
+    }
+    return id;
+}