scripts: kernel-doc: Restore anonymous enum parsing

The commit d38c8cfb ("scripts: kernel-doc: add support for typedef enum")
broke anonymous enum parsing. Restore it by relying on members rather than
its name.

Fixes: d38c8cfb

 ("scripts: kernel-doc: add support for typedef enum")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/20201102170637.36138-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>