py/mphal: Add stddef.h header for size_t.

yf13 · dpgeorge · commit ab4af2c1a615 · 2025-07-30T11:47:43.000+10:00
This includes "stddef.h" for `size_t` to resolve NuttX integration build
issues.

Signed-off-by: Yanfeng Liu &lt;yfliu2008@qq.com&gt;
diff --git a/py/mphal.h b/py/mphal.h
@@ -27,6 +27,7 @@
 #define MICROPY_INCLUDED_PY_MPHAL_H
 
 #include <stdint.h>
+#include <stddef.h>
 #include "py/mpconfig.h"
 
 #ifdef MICROPY_MPHALPORT_H
