Rename the global variable to avoid:

  tests/unit/test-coroutine.c:430:11: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
      bool *done = opaque;
            ^
  tests/unit/test-coroutine.c:438:10: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
      bool done = false;
           ^
  tests/unit/test-coroutine.c:198:12: note: previous declaration is here
  static int done;
             ^

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20231009100251.56019-11-philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>