tests: fix incorrect size_t format in benchmark-crypto

  $ make check-speed
  tests/benchmark-crypto-hash.c: In function 'test_hash_speed':
  tests/benchmark-crypto-hash.c:44:5: error: format '%ld' expects argument of type 'long int', but argument 2 has type 'size_t' [-Werror=format=]
       g_print("Testing chunk_size %ld bytes ", chunk_size);
       ^
  tests/benchmark-crypto-hash.c: In function 'main':
  tests/benchmark-crypto-hash.c:62:9: error: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'size_t' [-Werror=format=]
           snprintf(name, sizeof(name), "/crypto/hash/speed-%lu", i);
           ^
  cc1: all warnings being treated as errors
  rules.mak:66: recipe for target 'tests/benchmark-crypto-hash.o' failed
  make: *** [tests/benchmark-crypto-hash.o] Error 1

Reviewed-by: Longpeng(Mike) <longpeng@huawei.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
