qom/object_interfaces: Clean up global variable shadowing

qom/object_interfaces: Clean up global variable shadowing

Fix:

  qom/object_interfaces.c:262:53: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
  ObjectOptions *user_creatable_parse_str(const char *optarg, Error **errp)
                                                      ^
  qom/object_interfaces.c:298:46: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
  bool user_creatable_add_from_str(const char *optarg, Error **errp)
                                               ^
  qom/object_interfaces.c:313:49: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
  void user_creatable_process_cmdline(const char *optarg)
                                                  ^
  /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/getopt.h:77:14: note: previous declaration is here
  extern char *optarg;                    /* getopt(3) external variables */
               ^

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20231004120019.93101-9-philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>