mpy-cross: Don't use the internal printf functions.

They require mp_hal_stdout_tx_strn_cooked, which requires extra work to
add to mpy-cross.

mpy-cross/mpconfigport.h

@@ -59,6 +59,7 @@
 
 #define MICROPY_FLOAT_IMPL          (MICROPY_FLOAT_IMPL_DOUBLE)
 #define MICROPY_CPYTHON_COMPAT      (1)
+#define MICROPY_USE_INTERNAL_PRINTF (0)
 
 #define MICROPY_PY_BUILTINS_STR_UNICODE (1)