Add stdio header.

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

src/fs/low_flash.c

@@ -17,7 +17,8 @@
 
 #include "picokeys.h"
 #include "serial.h"
- #include "crypto_utils.h"
+#include "crypto_utils.h"
+#include <stdio.h>
 #ifdef PICO_PLATFORM
  #include "hardware/flash.h"
  #include "hardware/sync.h"

src/serial.c

@@ -21,6 +21,7 @@
 #if defined(ESP_PLATFORM)
 #include "esp_efuse.h"
 #endif
+#include <stdio.h>
 
 char pico_serial_str[2 * PICO_UNIQUE_BOARD_ID_SIZE_BYTES + 1];
 uint8_t pico_serial_hash[32];