py: Change type of .make_new and .call args: mp_uint_t becomes size_t.

This patch changes the type signature of .make_new and .call object method
slots to use size_t for n_args and n_kw (was mp_uint_t.  Makes code more
efficient when mp_uint_t is larger than a machine word.  Doesn't affect
ports when size_t and mp_uint_t have the same size.
diff --git a/py/objint.c b/py/objint.c
index 57fe364..7ee7653 100644
--- a/py/objint.c
+++ b/py/objint.c
@@ -42,7 +42,7 @@
 #endif
 
 // This dispatcher function is expected to be independent of the implementation of long int
-STATIC mp_obj_t mp_obj_int_make_new(mp_obj_t type_in, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args) {
+STATIC mp_obj_t mp_obj_int_make_new(mp_obj_t type_in, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     (void)type_in;
     mp_arg_check_num(n_args, n_kw, 0, 2, false);