contrib/plugins/lockstep: Fix string format

This fixes on Darwin:

  plugins/lockstep.c:138:25: warning: format specifies type 'unsigned long' but the argument has type 'uint64_t' (aka 'unsigned long long') [-Wformat]
                          us->pc, them->pc, g_slist_length(divergence_log),
                          ^~~~~~
  plugins/lockstep.c:138:33: warning: format specifies type 'unsigned long' but the argument has type 'uint64_t' (aka 'unsigned long long') [-Wformat]
                          us->pc, them->pc, g_slist_length(divergence_log),
                                  ^~~~~~~~
  plugins/lockstep.c:148:25: warning: format specifies type 'unsigned long' but the argument has type 'uint64_t' (aka 'unsigned long long') [-Wformat]
                          us->pc, us->insn_count, them->pc, them->insn_count);
                          ^~~~~~
  plugins/lockstep.c:148:49: warning: format specifies type 'unsigned long' but the argument has type 'uint64_t' (aka 'unsigned long long') [-Wformat]
                          us->pc, us->insn_count, them->pc, them->insn_count);
                                                  ^~~~~~~~
  plugins/lockstep.c:156:36: warning: format specifies type 'unsigned long' but the argument has type 'uint64_t' (aka 'unsigned long long') [-Wformat]
                                     prev->block->pc, prev->block->insns,
                                     ^~~~~~~~~~~~~~~
  plugins/lockstep.c:156:53: warning: format specifies type 'long' but the argument has type 'uint64_t' (aka 'unsigned long long') [-Wformat]
                                     prev->block->pc, prev->block->insns,
                                                      ^~~~~~~~~~~~~~~~~~

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20230907105004.88600-5-philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>