Adding unique_id variable.

Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>

hsm2040.h

@@ -10,6 +10,7 @@
 #include "ccid.h"
 #include "tusb.h"
 #include "file.h"
+#include "pico/unique_id.h"
 
 #define USB_REQ_CCID        0xA1
 
@@ -111,4 +112,6 @@ void put_binary (const char *s, int len);
 
 extern int flash_write_data_to_file(file_t *file, const uint8_t *data, uint16_t len);
 extern void low_flash_available();
+
+extern pico_unique_board_id_t unique_id;
 #endif