net: rename SOCK_ASYNC_NOSPACE and SOCK_ASYNC_WAITDATA

This patch is a cleanup to make following patch easier to
review.

Goal is to move SOCK_ASYNC_NOSPACE and SOCK_ASYNC_WAITDATA
from (struct socket)->flags to a (struct socket_wq)->flags
to benefit from RCU protection in sock_wake_async()

To ease backports, we rename both constants.

Two new helpers, sk_set_bit(int nr, struct sock *sk)
and sk_clear_bit(int net, struct sock *sk) are added so that
following patch can change their implementation.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/decnet/af_decnet.c b/net/decnet/af_decnet.c
index 675cf94..eebf5ac 100644
--- a/net/decnet/af_decnet.c
+++ b/net/decnet/af_decnet.c
@@ -1747,9 +1747,9 @@
 		}
 
 		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
-		set_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
+		sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
 		sk_wait_event(sk, &timeo, dn_data_ready(sk, queue, flags, target));
-		clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
+		sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
 		finish_wait(sk_sleep(sk), &wait);
 	}
 
@@ -2004,10 +2004,10 @@
 			}
 
 			prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
-			set_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
+			sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
 			sk_wait_event(sk, &timeo,
 				      !dn_queue_too_long(scp, queue, flags));
-			clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
+			sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
 			finish_wait(sk_sleep(sk), &wait);
 			continue;
 		}