afs: Fix kerneldoc warning shown up by W=1

Fix a kerneldoc warning in afs due to a partially documented internal
function by removing the kerneldoc marker.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-doc@vger.kernel.org
Link: https://lore.kernel.org/r/163214005516.2945267.7000234432243167892.stgit@warthog.procyon.org.uk/ # rfc v1
Link: https://lore.kernel.org/r/163281899704.2790286.9177774252843775348.stgit@warthog.procyon.org.uk/ # rfc v2

fs/afs/dir_silly.c

@@ -86,8 +86,8 @@ static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode
 	return afs_do_sync_operation(op);
 }
 
-/**
- * afs_sillyrename - Perform a silly-rename of a dentry
+/*
+ * Perform silly-rename of a dentry.
  *
  * AFS is stateless and the server doesn't know when the client is holding a
  * file open.  To prevent application problems when a file is unlinked while