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/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 87e9d79..3a37bd3 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -421,7 +421,7 @@
 
 	if (test_and_clear_bit(CF_APP_LIMITED, &con->flags)) {
 		con->sock->sk->sk_write_pending--;
-		clear_bit(SOCK_ASYNC_NOSPACE, &con->sock->flags);
+		clear_bit(SOCKWQ_ASYNC_NOSPACE, &con->sock->flags);
 	}
 
 	if (!test_and_set_bit(CF_WRITE_PENDING, &con->flags))
@@ -1448,7 +1448,7 @@
 					      msg_flags);
 			if (ret == -EAGAIN || ret == 0) {
 				if (ret == -EAGAIN &&
-				    test_bit(SOCK_ASYNC_NOSPACE, &con->sock->flags) &&
+				    test_bit(SOCKWQ_ASYNC_NOSPACE, &con->sock->flags) &&
 				    !test_and_set_bit(CF_APP_LIMITED, &con->flags)) {
 					/* Notify TCP that we're limited by the
 					 * application window size.