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/socket.c b/net/socket.c
index dd2c247..16be908 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1072,11 +1072,11 @@
 	}
 	switch (how) {
 	case SOCK_WAKE_WAITD:
-		if (test_bit(SOCK_ASYNC_WAITDATA, &sock->flags))
+		if (test_bit(SOCKWQ_ASYNC_WAITDATA, &sock->flags))
 			break;
 		goto call_kill;
 	case SOCK_WAKE_SPACE:
-		if (!test_and_clear_bit(SOCK_ASYNC_NOSPACE, &sock->flags))
+		if (!test_and_clear_bit(SOCKWQ_ASYNC_NOSPACE, &sock->flags))
 			break;
 		/* fall through */
 	case SOCK_WAKE_IO: