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/core/sock.c b/net/core/sock.c
index 1e4dd54..9d79569 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1815,7 +1815,7 @@
 {
 	DEFINE_WAIT(wait);
 
-	clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
+	sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 	for (;;) {
 		if (!timeo)
 			break;
@@ -1861,7 +1861,7 @@
 		if (sk_wmem_alloc_get(sk) < sk->sk_sndbuf)
 			break;
 
-		set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
+		sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 		err = -EAGAIN;
 		if (!timeo)
@@ -2048,9 +2048,9 @@
 	DEFINE_WAIT(wait);
 
 	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);
 	rc = sk_wait_event(sk, timeo, skb_peek_tail(&sk->sk_receive_queue) != skb);
-	clear_bit(SOCK_ASYNC_WAITDATA, &sk->sk_socket->flags);
+	sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
 	finish_wait(sk_sleep(sk), &wait);
 	return rc;
 }