kernel-doc: fix unnamed struct/union warning

Fix kernel-doc warning:
Warning(linux-2.6.22-rc2-git2/include/linux/skbuff.h:316): No description found for parameter '}'

which is caused by nested anonymous structs/unions ending with:
  };
};

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>