tcp: add missing htmldocs for skb->ll_node and sk->defer_list

Add missing entries to fix these "make htmldocs" warnings.

./include/linux/skbuff.h:953: warning: Function parameter or member 'll_node' not described in 'sk_buff'
./include/net/sock.h:540: warning: Function parameter or member 'defer_list' not described in 'sock'

Fixes: f35f821 ("tcp: defer skb freeing after socket lock is released")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -627,6 +627,7 @@ typedef unsigned char *sk_buff_data_t;
  *		for retransmit timer
  *	@rbnode: RB tree node, alternative to next/prev for netem/tcp
  *	@list: queue head
+ *	@ll_node: anchor in an llist (eg socket defer_list)
  *	@sk: Socket we are owned by
  *	@ip_defrag_offset: (aka @sk) alternate use of @sk, used in
  *		fragmentation management

include/net/sock.h

@@ -292,6 +292,7 @@ struct bpf_local_storage;
   *	@sk_pacing_shift: scaling factor for TCP Small Queues
   *	@sk_lingertime: %SO_LINGER l_linger setting
   *	@sk_backlog: always used with the per-socket spinlock held
+  *	@defer_list: head of llist storing skbs to be freed
   *	@sk_callback_lock: used with the callbacks in the end of this struct
   *	@sk_error_queue: rarely used
   *	@sk_prot_creator: sk_prot of original sock creator (see ipv6_setsockopt,