crypto/sm2/sm2_sign.c: ensure UINT16_MAX is properly defined
Fixes
#include "internal/sm2.h"
#include "internal/sm2err.h"
#include "internal/ec_int.h" /* ec_group_do_inverse_ord() */
+#include "internal/numbers.h"
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/err.h>
