fix: add stdint.h as stdio.h providing only necessary types

due to newlib version 4.2.0 provided within
arm-none-eabi-gcc-12.2.1

See:
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git

Title: In <stdio.h> provide only necessary types
Commit: 357d7fcc6ad1b0660e2b3131d09eb22e2559e46d

Signed-off-by: Frederic Pillon <[email protected]>

Author: fpistm

cores/arduino/avr/dtostrf.c

@@ -19,6 +19,7 @@
 */
 
 #include <stdio.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>