system/physmem: Fix reference to dump-guest-core

dump_guest_core is exposed as dump-guest-core with QOM.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-ID: <20240628-dump-v1-1-c581d10f3646@daynix.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

system/physmem.c

@@ -1521,7 +1521,7 @@ static void qemu_ram_setup_dump(void *addr, ram_addr_t size)
         if (ret) {
             perror("qemu_madvise");
             fprintf(stderr, "madvise doesn't support MADV_DONTDUMP, "
-                            "but dump_guest_core=off specified\n");
+                            "but dump-guest-core=off specified\n");
         }
     }
 }